diff --git a/packages/react-resizable-panels-website/src/routes/EndToEndTesting/index.tsx b/packages/react-resizable-panels-website/src/routes/EndToEndTesting/index.tsx
index 549bf34c9..c3562e61d 100644
--- a/packages/react-resizable-panels-website/src/routes/EndToEndTesting/index.tsx
+++ b/packages/react-resizable-panels-website/src/routes/EndToEndTesting/index.tsx
@@ -9,7 +9,6 @@ import {
 import {
   ImperativePanelGroupHandle,
   ImperativePanelHandle,
-  MixedSizes,
 } from "react-resizable-panels";
 
 import { urlPanelGroupToPanelGroup, urlToUrlData } from "../../utils/UrlData";
diff --git a/packages/react-resizable-panels-website/src/routes/examples/ImperativePanelGroupApi.tsx b/packages/react-resizable-panels-website/src/routes/examples/ImperativePanelGroupApi.tsx
index 834be01fd..260eca08c 100644
--- a/packages/react-resizable-panels-website/src/routes/examples/ImperativePanelGroupApi.tsx
+++ b/packages/react-resizable-panels-website/src/routes/examples/ImperativePanelGroupApi.tsx
@@ -1,8 +1,5 @@
 import { useRef, useState } from "react";
-import type {
-  ImperativePanelGroupHandle,
-  MixedSizes,
-} from "react-resizable-panels";
+import type { ImperativePanelGroupHandle } from "react-resizable-panels";
 import { Panel, PanelGroup } from "react-resizable-panels";
 
 import { ResizeHandle } from "../../components/ResizeHandle";
diff --git a/packages/react-resizable-panels-website/src/routes/examples/types.ts b/packages/react-resizable-panels-website/src/routes/examples/types.ts
index 3de2d2dde..d04b369ed 100644
--- a/packages/react-resizable-panels-website/src/routes/examples/types.ts
+++ b/packages/react-resizable-panels-website/src/routes/examples/types.ts
@@ -1,5 +1,3 @@
-import { MixedSizes } from "react-resizable-panels";
-
 export type PanelCollapseLogEntryType = "onCollapse";
 export type PanelExpandLogEntryType = "onExpand";
 export type PanelGroupLayoutLogEntryType = "onLayout";
@@ -21,12 +19,12 @@ export type PanelResizeHandleDraggingLogEntry = {
 };
 export type PanelGroupLayoutLogEntry = {
   groupId: string;
-  layout: MixedSizes[];
+  layout: number[];
   type: PanelGroupLayoutLogEntryType;
 };
 export type PanelResizeLogEntry = {
   panelId: string;
-  size: MixedSizes;
+  size: number;
   type: PanelResizeLogEntryType;
 };
 
diff --git a/packages/react-resizable-panels-website/src/utils/UrlData.ts b/packages/react-resizable-panels-website/src/utils/UrlData.ts
index 1bf27a72b..c919261b1 100644
--- a/packages/react-resizable-panels-website/src/utils/UrlData.ts
+++ b/packages/react-resizable-panels-website/src/utils/UrlData.ts
@@ -9,7 +9,6 @@ import {
 import {
   ImperativePanelGroupHandle,
   ImperativePanelHandle,
-  MixedSizes,
   Panel,
   PanelGroup,
   PanelGroupOnLayout,
@@ -183,7 +182,7 @@ function urlPanelToPanel(
       }
     };
 
-    onResize = (size: MixedSizes) => {
+    onResize = (size: number) => {
       const debugLog = debugLogRef.current;
       if (debugLog) {
         debugLog.log({
@@ -248,7 +247,7 @@ export function urlPanelGroupToPanelGroup(
 
   const groupId = urlPanelGroup.id;
   if (groupId) {
-    onLayout = (layout: MixedSizes[]) => {
+    onLayout = (layout: number[]) => {
       const debugLog = debugLogRef.current;
       if (debugLog) {
         debugLog.log({ groupId, type: "onLayout", layout });
diff --git a/packages/react-resizable-panels-website/tests/utils/panels.ts b/packages/react-resizable-panels-website/tests/utils/panels.ts
index f1e9dc1e3..46b07381a 100644
--- a/packages/react-resizable-panels-website/tests/utils/panels.ts
+++ b/packages/react-resizable-panels-website/tests/utils/panels.ts
@@ -2,7 +2,6 @@ import { Locator, Page, expect } from "@playwright/test";
 import { assert } from "./assert";
 import { getBodyCursorStyle } from "./cursor";
 import { verifyFuzzySizesPercentages } from "./verify";
-import { Size } from "react-resizable-panels";
 
 type Operation = {
   expectedCursor?: string;
@@ -150,7 +149,7 @@ export async function dragResizeTo(
 export async function imperativeResizePanel(
   page: Page,
   panelId: string,
-  size: Size
+  size: number
 ) {
   const panelIdSelect = page.locator("#panelIdSelect");
   await panelIdSelect.selectOption(panelId);
diff --git a/packages/react-resizable-panels/CHANGELOG.md b/packages/react-resizable-panels/CHANGELOG.md
index e16a8ecd9..0133cf5bd 100644
--- a/packages/react-resizable-panels/CHANGELOG.md
+++ b/packages/react-resizable-panels/CHANGELOG.md
@@ -1,5 +1,10 @@
 # Changelog
 
+## 1.0.0-rc.1
+
+- Remove support for pixel-based Panel constraints; props like `defaultSizePercentage` should now be `defaultSize`
+- Replaced `dataAttributes` prop with `...rest` prop that supports all HTML attributes
+
 ## 0.0.63
 
 - Change default (not-yet-registered) Panel flex-grow style from 0 to 1
diff --git a/packages/react-resizable-panels/src/Panel.test.tsx b/packages/react-resizable-panels/src/Panel.test.tsx
index 7dc14abc6..c81b3765e 100644
--- a/packages/react-resizable-panels/src/Panel.test.tsx
+++ b/packages/react-resizable-panels/src/Panel.test.tsx
@@ -1,12 +1,8 @@
+import assert from "assert";
 import { Root, createRoot } from "react-dom/client";
 import { act } from "react-dom/test-utils";
-import {
-  ImperativePanelHandle,
-  MixedSizes,
-  Panel,
-  PanelGroup,
-  PanelResizeHandle,
-} from ".";
+import { ImperativePanelHandle, Panel, PanelGroup, PanelResizeHandle } from ".";
+import { getPanelElement } from "./utils/dom/getPanelElement";
 import {
   mockPanelGroupOffsetWidthAndHeight,
   verifyExpandedPanelGroupLayout,
@@ -66,7 +62,7 @@ describe("PanelGroup", () => {
       let leftPanelRef = createRef<ImperativePanelHandle>();
       let rightPanelRef = createRef<ImperativePanelHandle>();
 
-      let mostRecentLayout: MixedSizes[] | null;
+      let mostRecentLayout: number[] | null;
 
       beforeEach(() => {
         leftPanelRef = createRef<ImperativePanelHandle>();
@@ -74,7 +70,7 @@ describe("PanelGroup", () => {
 
         mostRecentLayout = null;
 
-        const onLayout = (layout: MixedSizes[]) => {
+        const onLayout = (layout: number[]) => {
           mostRecentLayout = layout;
         };
 
@@ -135,7 +131,7 @@ describe("PanelGroup", () => {
       let middlePanelRef = createRef<ImperativePanelHandle>();
       let rightPanelRef = createRef<ImperativePanelHandle>();
 
-      let mostRecentLayout: MixedSizes[] | null;
+      let mostRecentLayout: number[] | null;
 
       beforeEach(() => {
         leftPanelRef = createRef<ImperativePanelHandle>();
@@ -144,7 +140,7 @@ describe("PanelGroup", () => {
 
         mostRecentLayout = null;
 
-        const onLayout = (layout: MixedSizes[]) => {
+        const onLayout = (layout: number[]) => {
           mostRecentLayout = layout;
         };
 
@@ -227,6 +223,24 @@ describe("PanelGroup", () => {
     });
   });
 
+  it("should support ...rest attributes", () => {
+    act(() => {
+      root.render(
+        <PanelGroup direction="horizontal">
+          <Panel data-test-name="foo" id="panel" tabIndex={123} title="bar" />
+          <PanelResizeHandle />
+          <Panel />
+        </PanelGroup>
+      );
+    });
+
+    const element = getPanelElement("panel");
+    assert(element);
+    expect(element.tabIndex).toBe(123);
+    expect(element.getAttribute("data-test-name")).toBe("foo");
+    expect(element.title).toBe("bar");
+  });
+
   describe("DEV warnings", () => {
     it("should warn about server rendered panels with no default size", () => {
       jest.resetModules();
diff --git a/packages/react-resizable-panels/src/Panel.ts b/packages/react-resizable-panels/src/Panel.ts
index 887defcfa..be9ba9d27 100644
--- a/packages/react-resizable-panels/src/Panel.ts
+++ b/packages/react-resizable-panels/src/Panel.ts
@@ -3,10 +3,10 @@ import { isDevelopment } from "#is-development";
 import { PanelGroupContext } from "./PanelGroupContext";
 import useIsomorphicLayoutEffect from "./hooks/useIsomorphicEffect";
 import useUniqueId from "./hooks/useUniqueId";
-import { DataAttributes, Size } from "./types";
 import {
   ElementType,
   ForwardedRef,
+  HTMLAttributes,
   PropsWithChildren,
   createElement,
   forwardRef,
@@ -18,8 +18,8 @@ import {
 export type PanelOnCollapse = () => void;
 export type PanelOnExpand = () => void;
 export type PanelOnResize = (
-  mixedSizes: Size,
-  prevMixedSizes: Size | undefined
+  size: number,
+  prevSize: number | undefined
 ) => void;
 
 export type PanelCallbacks = {
@@ -48,35 +48,34 @@ export type ImperativePanelHandle = {
   collapse: () => void;
   expand: () => void;
   getId(): string;
-  getSize(): Size;
+  getSize(): number;
   isCollapsed: () => boolean;
   isExpanded: () => boolean;
-  resize: (size: Partial<Size>) => void;
+  resize: (size: number) => void;
 };
 
-export type PanelProps = PropsWithChildren<{
-  className?: string;
-  collapsedSize?: number | undefined;
-  collapsible?: boolean | undefined;
-  dataAttributes?: DataAttributes;
-  defaultSize?: number | undefined;
-  id?: string;
-  maxSize?: number | undefined;
-  minSize?: number | undefined;
-  onCollapse?: PanelOnCollapse;
-  onExpand?: PanelOnExpand;
-  onResize?: PanelOnResize;
-  order?: number;
-  style?: object;
-  tagName?: ElementType;
-}>;
+export type PanelProps = Omit<HTMLAttributes<ElementType>, "id" | "onResize"> &
+  PropsWithChildren<{
+    className?: string;
+    collapsedSize?: number | undefined;
+    collapsible?: boolean | undefined;
+    defaultSize?: number | undefined;
+    id?: string;
+    maxSize?: number | undefined;
+    minSize?: number | undefined;
+    onCollapse?: PanelOnCollapse;
+    onExpand?: PanelOnExpand;
+    onResize?: PanelOnResize;
+    order?: number;
+    style?: object;
+    tagName?: ElementType;
+  }>;
 
 export function PanelWithForwardedRef({
   children,
   className: classNameFromProps = "",
   collapsedSize,
   collapsible,
-  dataAttributes,
   defaultSize,
   forwardedRef,
   id: idFromProps,
@@ -88,6 +87,7 @@ export function PanelWithForwardedRef({
   order,
   style: styleFromProps,
   tagName: Type = "div",
+  ...rest
 }: PanelProps & {
   forwardedRef: ForwardedRef<ImperativePanelHandle>;
 }) {
@@ -198,8 +198,8 @@ export function PanelWithForwardedRef({
       isExpanded() {
         return !isPanelCollapsed(panelDataRef.current);
       },
-      resize: (mixedSizes: Partial<Size>) => {
-        resizePanel(panelDataRef.current, mixedSizes);
+      resize: (size: number) => {
+        resizePanel(panelDataRef.current, size);
       },
     }),
     [
@@ -215,6 +215,8 @@ export function PanelWithForwardedRef({
   const style = getPanelStyle(panelDataRef.current);
 
   return createElement(Type, {
+    ...rest,
+
     children,
     className: classNameFromProps,
     style: {
@@ -222,8 +224,6 @@ export function PanelWithForwardedRef({
       ...styleFromProps,
     },
 
-    ...dataAttributes,
-
     // CSS selectors
     "data-panel": "",
     "data-panel-id": panelId,
diff --git a/packages/react-resizable-panels/src/PanelGroup.test.tsx b/packages/react-resizable-panels/src/PanelGroup.test.tsx
index 11ac72296..1aeb6147f 100644
--- a/packages/react-resizable-panels/src/PanelGroup.test.tsx
+++ b/packages/react-resizable-panels/src/PanelGroup.test.tsx
@@ -2,13 +2,14 @@ import { Root, createRoot } from "react-dom/client";
 import { act } from "react-dom/test-utils";
 import {
   ImperativePanelGroupHandle,
-  MixedSizes,
   Panel,
   PanelGroup,
   PanelResizeHandle,
 } from ".";
 import { mockPanelGroupOffsetWidthAndHeight } from "./utils/test-utils";
 import { createRef } from "./vendor/react";
+import { getPanelGroupElement } from "./utils/dom/getPanelGroupElement";
+import assert from "assert";
 
 describe("PanelGroup", () => {
   let expectedWarnings: string[] = [];
@@ -79,9 +80,9 @@ describe("PanelGroup", () => {
     it("should get and set layouts", () => {
       const ref = createRef<ImperativePanelGroupHandle>();
 
-      let mostRecentLayout: MixedSizes[] | null = null;
+      let mostRecentLayout: number[] | null = null;
 
-      const onLayout = (layout: MixedSizes[]) => {
+      const onLayout = (layout: number[]) => {
         mostRecentLayout = layout;
       };
 
@@ -105,6 +106,30 @@ describe("PanelGroup", () => {
     });
   });
 
+  it("should support ...rest attributes", () => {
+    act(() => {
+      root.render(
+        <PanelGroup
+          data-test-name="foo"
+          direction="horizontal"
+          id="group"
+          tabIndex={123}
+          title="bar"
+        >
+          <Panel />
+          <PanelResizeHandle />
+          <Panel />
+        </PanelGroup>
+      );
+    });
+
+    const element = getPanelGroupElement("group");
+    assert(element);
+    expect(element.tabIndex).toBe(123);
+    expect(element.getAttribute("data-test-name")).toBe("foo");
+    expect(element.title).toBe("bar");
+  });
+
   describe("DEV warnings", () => {
     it("should warn about unstable layouts without id and order props", () => {
       act(() => {
diff --git a/packages/react-resizable-panels/src/PanelGroup.ts b/packages/react-resizable-panels/src/PanelGroup.ts
index 6c0852508..9b5c96d99 100644
--- a/packages/react-resizable-panels/src/PanelGroup.ts
+++ b/packages/react-resizable-panels/src/PanelGroup.ts
@@ -4,7 +4,7 @@ import { DragState, PanelGroupContext, ResizeEvent } from "./PanelGroupContext";
 import useIsomorphicLayoutEffect from "./hooks/useIsomorphicEffect";
 import useUniqueId from "./hooks/useUniqueId";
 import { useWindowSplitterPanelGroupBehavior } from "./hooks/useWindowSplitterPanelGroupBehavior";
-import { DataAttributes, Direction, Size } from "./types";
+import { Direction } from "./types";
 import { adjustLayoutByDelta } from "./utils/adjustLayoutByDelta";
 import { areEqual } from "./utils/arrays";
 import { calculateDeltaPercentage } from "./utils/calculateDeltaPercentage";
@@ -27,6 +27,7 @@ import {
   CSSProperties,
   ElementType,
   ForwardedRef,
+  HTMLAttributes,
   PropsWithChildren,
   createElement,
   forwardRef,
@@ -42,8 +43,8 @@ const LOCAL_STORAGE_DEBOUNCE_INTERVAL = 100;
 
 export type ImperativePanelGroupHandle = {
   getId: () => string;
-  getLayout: () => Size[];
-  setLayout: (layout: Partial<Size>[]) => void;
+  getLayout: () => number[];
+  setLayout: (layout: number[]) => void;
 };
 
 export type PanelGroupStorage = {
@@ -51,7 +52,7 @@ export type PanelGroupStorage = {
   setItem(name: string, value: string): void;
 };
 
-export type PanelGroupOnLayout = (layout: Size[]) => void;
+export type PanelGroupOnLayout = (layout: number[]) => void;
 
 const defaultStorage: PanelGroupStorage = {
   getItem: (name: string) => {
@@ -64,18 +65,18 @@ const defaultStorage: PanelGroupStorage = {
   },
 };
 
-export type PanelGroupProps = PropsWithChildren<{
-  autoSaveId?: string | null;
-  className?: string;
-  dataAttributes?: DataAttributes;
-  direction: Direction;
-  id?: string | null;
-  keyboardResizeBy?: number | null;
-  onLayout?: PanelGroupOnLayout | null;
-  storage?: PanelGroupStorage;
-  style?: CSSProperties;
-  tagName?: ElementType;
-}>;
+export type PanelGroupProps = Omit<HTMLAttributes<ElementType>, "id"> &
+  PropsWithChildren<{
+    autoSaveId?: string | null;
+    className?: string;
+    direction: Direction;
+    id?: string | null;
+    keyboardResizeBy?: number | null;
+    onLayout?: PanelGroupOnLayout | null;
+    storage?: PanelGroupStorage;
+    style?: CSSProperties;
+    tagName?: ElementType;
+  }>;
 
 const debounceMap: {
   [key: string]: typeof savePanelGroupLayout;
@@ -86,15 +87,15 @@ function PanelGroupWithForwardedRef({
   autoSaveId = null,
   children,
   className: classNameFromProps = "",
-  dataAttributes,
   direction,
   forwardedRef,
-  id: idFromProps,
+  id: idFromProps = null,
   onLayout = null,
   keyboardResizeBy = null,
   storage = defaultStorage,
   style: styleFromProps,
   tagName: Type = "div",
+  ...rest
 }: PanelGroupProps & {
   forwardedRef: ForwardedRef<ImperativePanelGroupHandle>;
 }) {
@@ -103,7 +104,7 @@ function PanelGroupWithForwardedRef({
   const [dragState, setDragState] = useState<DragState | null>(null);
   const [layout, setLayout] = useState<number[]>([]);
 
-  const panelIdToLastNotifiedSizeMapRef = useRef<Record<string, Size>>({});
+  const panelIdToLastNotifiedSizeMapRef = useRef<Record<string, number>>({});
   const panelSizeBeforeCollapseRef = useRef<Map<string, number>>(new Map());
   const prevDeltaRef = useRef<number>(0);
 
@@ -152,7 +153,7 @@ function PanelGroupWithForwardedRef({
 
         return layout;
       },
-      setLayout: (unsafeLayout: Size[]) => {
+      setLayout: (unsafeLayout: number[]) => {
         const { onLayout } = committedValuesRef.current;
         const { layout: prevLayout, panelDataArray } = eagerValuesRef.current;
 
@@ -826,6 +827,8 @@ function PanelGroupWithForwardedRef({
     PanelGroupContext.Provider,
     { value: context },
     createElement(Type, {
+      ...rest,
+
       children,
       className: classNameFromProps,
       style: {
@@ -833,8 +836,6 @@ function PanelGroupWithForwardedRef({
         ...styleFromProps,
       },
 
-      ...dataAttributes,
-
       // CSS selectors
       "data-panel-group": "",
       "data-panel-group-direction": direction,
diff --git a/packages/react-resizable-panels/src/PanelGroupContext.ts b/packages/react-resizable-panels/src/PanelGroupContext.ts
index 772a33e62..094061344 100644
--- a/packages/react-resizable-panels/src/PanelGroupContext.ts
+++ b/packages/react-resizable-panels/src/PanelGroupContext.ts
@@ -1,5 +1,4 @@
 import { PanelData } from "./Panel";
-import { Size } from "./types";
 import { CSSProperties, createContext } from "./vendor/react";
 
 export type ResizeEvent = KeyboardEvent | MouseEvent | TouchEvent;
@@ -17,14 +16,14 @@ export const PanelGroupContext = createContext<{
   direction: "horizontal" | "vertical";
   dragState: DragState | null;
   expandPanel: (panelData: PanelData) => void;
-  getPanelSize: (panelData: PanelData) => Size;
+  getPanelSize: (panelData: PanelData) => number;
   getPanelStyle: (panelData: PanelData) => CSSProperties;
   groupId: string;
   isPanelCollapsed: (panelData: PanelData) => boolean;
   isPanelExpanded: (panelData: PanelData) => boolean;
   registerPanel: (panelData: PanelData) => void;
   registerResizeHandle: (dragHandleId: string) => ResizeHandler;
-  resizePanel: (panelData: PanelData, mixedSizes: Partial<Size>) => void;
+  resizePanel: (panelData: PanelData, size: number) => void;
   startDragging: (dragHandleId: string, event: ResizeEvent) => void;
   stopDragging: () => void;
   unregisterPanel: (panelData: PanelData) => void;
diff --git a/packages/react-resizable-panels/src/PanelResizeHandle.test.tsx b/packages/react-resizable-panels/src/PanelResizeHandle.test.tsx
new file mode 100644
index 000000000..f088e43a9
--- /dev/null
+++ b/packages/react-resizable-panels/src/PanelResizeHandle.test.tsx
@@ -0,0 +1,68 @@
+import assert from "assert";
+import { Root, createRoot } from "react-dom/client";
+import { act } from "react-dom/test-utils";
+import { Panel, PanelGroup, PanelResizeHandle } from ".";
+import { getResizeHandleElement } from "./utils/dom/getResizeHandleElement";
+
+describe("PanelResizeHandle", () => {
+  let expectedWarnings: string[] = [];
+  let root: Root;
+
+  beforeEach(() => {
+    // @ts-expect-error
+    global.IS_REACT_ACT_ENVIRONMENT = true;
+
+    const container = document.createElement("div");
+    document.body.appendChild(container);
+
+    expectedWarnings = [];
+    root = createRoot(container);
+
+    jest.spyOn(console, "warn").mockImplementation((actualMessage: string) => {
+      const match = expectedWarnings.findIndex((expectedMessage) => {
+        return actualMessage.includes(expectedMessage);
+      });
+
+      if (match >= 0) {
+        expectedWarnings.splice(match, 1);
+        return;
+      }
+
+      throw Error(`Unexpected warning: ${actualMessage}`);
+    });
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+    jest.resetModules();
+
+    act(() => {
+      root.unmount();
+    });
+
+    expect(expectedWarnings).toHaveLength(0);
+  });
+
+  it("should support ...rest attributes", () => {
+    act(() => {
+      root.render(
+        <PanelGroup direction="horizontal">
+          <Panel />
+          <PanelResizeHandle
+            data-test-name="foo"
+            id="handle"
+            tabIndex={123}
+            title="bar"
+          />
+          <Panel />
+        </PanelGroup>
+      );
+    });
+
+    const element = getResizeHandleElement("handle");
+    assert(element);
+    expect(element.tabIndex).toBe(123);
+    expect(element.getAttribute("data-test-name")).toBe("foo");
+    expect(element.title).toBe("bar");
+  });
+});
diff --git a/packages/react-resizable-panels/src/PanelResizeHandle.ts b/packages/react-resizable-panels/src/PanelResizeHandle.ts
index 520b61dce..ac8daf27d 100644
--- a/packages/react-resizable-panels/src/PanelResizeHandle.ts
+++ b/packages/react-resizable-panels/src/PanelResizeHandle.ts
@@ -3,8 +3,9 @@ import {
   createElement,
   CSSProperties,
   ElementType,
+  HTMLAttributes,
+  PropsWithChildren,
   MouseEvent as ReactMouseEvent,
-  ReactNode,
   TouchEvent,
   useCallback,
   useContext,
@@ -20,30 +21,30 @@ import {
   ResizeHandler,
 } from "./PanelGroupContext";
 import { getCursorStyle } from "./utils/cursor";
-import { DataAttributes } from "./types";
 
 export type PanelResizeHandleOnDragging = (isDragging: boolean) => void;
 
-export type PanelResizeHandleProps = {
-  children?: ReactNode;
-  className?: string;
-  dataAttributes?: DataAttributes;
-  disabled?: boolean;
-  id?: string | null;
-  onDragging?: PanelResizeHandleOnDragging;
-  style?: CSSProperties;
-  tagName?: ElementType;
-};
+export type PanelResizeHandleProps = Omit<HTMLAttributes<ElementType>, "id"> &
+  PropsWithChildren<{
+    className?: string;
+    disabled?: boolean;
+    id?: string | null;
+    onDragging?: PanelResizeHandleOnDragging;
+    style?: CSSProperties;
+    tabIndex?: number;
+    tagName?: ElementType;
+  }>;
 
 export function PanelResizeHandle({
   children = null,
   className: classNameFromProps = "",
-  dataAttributes,
   disabled = false,
-  id: idFromProps = null,
+  id: idFromProps,
   onDragging,
   style: styleFromProps = {},
+  tabIndex = 0,
   tagName: Type = "div",
+  ...rest
 }: PanelResizeHandleProps) {
   const divElementRef = useRef<HTMLDivElement>(null);
 
@@ -152,6 +153,8 @@ export function PanelResizeHandle({
   };
 
   return createElement(Type, {
+    ...rest,
+
     children,
     className: classNameFromProps,
     onBlur: () => setIsFocused(false),
@@ -181,9 +184,7 @@ export function PanelResizeHandle({
       ...style,
       ...styleFromProps,
     },
-    tabIndex: 0,
-
-    ...dataAttributes,
+    tabIndex,
 
     // CSS selectors
     "data-panel-group-direction": direction,
diff --git a/packages/react-resizable-panels/src/index.ts b/packages/react-resizable-panels/src/index.ts
index be8a53d0c..d5a42906a 100644
--- a/packages/react-resizable-panels/src/index.ts
+++ b/packages/react-resizable-panels/src/index.ts
@@ -2,8 +2,6 @@ import { Panel } from "./Panel";
 import { PanelGroup } from "./PanelGroup";
 import { PanelResizeHandle } from "./PanelResizeHandle";
 
-import type { Size } from "./types";
-
 import type {
   ImperativePanelHandle,
   PanelOnCollapse,
@@ -26,7 +24,6 @@ export {
   // TypeScript types
   ImperativePanelGroupHandle,
   ImperativePanelHandle,
-  Size as MixedSizes,
   PanelGroupOnLayout,
   PanelGroupProps,
   PanelGroupStorage,
@@ -36,7 +33,6 @@ export {
   PanelProps,
   PanelResizeHandleOnDragging,
   PanelResizeHandleProps,
-  Size,
 
   // React components
   Panel,
diff --git a/packages/react-resizable-panels/src/types.ts b/packages/react-resizable-panels/src/types.ts
index 7abdbe185..ef9ffc8ce 100644
--- a/packages/react-resizable-panels/src/types.ts
+++ b/packages/react-resizable-panels/src/types.ts
@@ -1,10 +1,4 @@
 export type Direction = "horizontal" | "vertical";
 
-export type Size = number;
-
 export type ResizeEvent = KeyboardEvent | MouseEvent | TouchEvent;
 export type ResizeHandler = (event: ResizeEvent) => void;
-
-export type DataAttributes = {
-  [attribute: string]: string | number | boolean | undefined;
-};
diff --git a/packages/react-resizable-panels/src/utils/callPanelCallbacks.ts b/packages/react-resizable-panels/src/utils/callPanelCallbacks.ts
index 689928408..a8831a4d3 100644
--- a/packages/react-resizable-panels/src/utils/callPanelCallbacks.ts
+++ b/packages/react-resizable-panels/src/utils/callPanelCallbacks.ts
@@ -1,11 +1,10 @@
 import { PanelData } from "../Panel";
-import { Size } from "../types";
 
 // Layout should be pre-converted into percentages
 export function callPanelCallbacks(
   panelsArray: PanelData[],
   layout: number[],
-  panelIdToLastNotifiedMixedSizesMap: Record<string, Size>
+  panelIdToLastNotifiedSizeMap: Record<string, number>
 ) {
   layout.forEach((size, index) => {
     const panelData = panelsArray[index];
@@ -19,9 +18,9 @@ export function callPanelCallbacks(
     const { callbacks, constraints, id: panelId } = panelData;
     const { collapsedSize = 0, collapsible } = constraints;
 
-    const lastNotifiedSize = panelIdToLastNotifiedMixedSizesMap[panelId];
+    const lastNotifiedSize = panelIdToLastNotifiedSizeMap[panelId];
     if (lastNotifiedSize == null || size !== lastNotifiedSize) {
-      panelIdToLastNotifiedMixedSizesMap[panelId] = size;
+      panelIdToLastNotifiedSizeMap[panelId] = size;
 
       const { onCollapse, onExpand, onResize } = callbacks;
 
diff --git a/packages/react-resizable-panels/src/utils/test-utils.ts b/packages/react-resizable-panels/src/utils/test-utils.ts
index 3b699d1af..7491229f6 100644
--- a/packages/react-resizable-panels/src/utils/test-utils.ts
+++ b/packages/react-resizable-panels/src/utils/test-utils.ts
@@ -1,5 +1,3 @@
-import { Size } from "../types";
-
 const util = require("util");
 
 export function expectToBeCloseToArray(
@@ -74,7 +72,7 @@ export function mockPanelGroupOffsetWidthAndHeight(
 }
 
 export function verifyExpandedPanelGroupLayout(
-  actualLayout: Size[],
+  actualLayout: number[],
   expectedLayout: number[]
 ) {
   expect(actualLayout).toEqual(expectedLayout);
diff --git a/packages/react-resizable-panels/src/vendor/react.ts b/packages/react-resizable-panels/src/vendor/react.ts
index a0f3d73cb..cffb0fb3e 100644
--- a/packages/react-resizable-panels/src/vendor/react.ts
+++ b/packages/react-resizable-panels/src/vendor/react.ts
@@ -12,6 +12,7 @@ import type {
   CSSProperties,
   ElementType,
   ForwardedRef,
+  HTMLAttributes,
   MouseEvent,
   PropsWithChildren,
   ReactNode,
@@ -57,6 +58,7 @@ export type {
   CSSProperties,
   ElementType,
   ForwardedRef,
+  HTMLAttributes,
   MouseEvent,
   PropsWithChildren,
   ReactNode,