diff --git a/external_chi2/optimal_observables/interface_oos_161.py b/external_chi2/optimal_observables/interface_oos_161.py
deleted file mode 100644
index 700da71..0000000
--- a/external_chi2/optimal_observables/interface_oos_161.py
+++ /dev/null
@@ -1,47 +0,0 @@
-import numpy as np
-import pathlib
-import jax.numpy as jnp
-
-current_file_path = pathlib.Path(__file__).resolve().parent
-
-# future colliders to include
-collider = "FCCee"
-
-
-class OptimalWW161:
-    def __init__(self, coefficients, rgemat=None):
-        oo_wc_basis = ["OpD", "OpWB", "OWWW", "Opl1", "Ope", "O3pl1"]
-
-        self.project = np.zeros((len(oo_wc_basis), coefficients.size))
-        for i, op in enumerate(oo_wc_basis):
-            if op in coefficients.name:
-                self.project[i, np.argwhere(coefficients.name == op)[0, 0]] = 1
-
-        self.datasets = {
-            "{collider}_ww_lepto_161": "invcov_{collider}_ww_leptonic_161.dat",
-            "{collider}_ww_semilep_161": "invcov_{collider}_ww_semilep_161.dat",
-        }
-
-        incovs_reordered = []
-        for path in self.datasets.values():
-            invcov = np.loadtxt(current_file_path / path.format(collider=collider))
-            temp = jnp.einsum("ij, jk, kl", self.project.T, invcov, self.project)
-            incovs_reordered.append(temp)
-        self.incov_tot = jnp.sum(jnp.array(incovs_reordered), axis=0)
-
-        self.rgemat = rgemat
-
-        if self.rgemat is not None:
-            # multiply the RGE matrix as well
-            self.incov_tot = jnp.einsum(
-                "ij, jk, kl", self.rgemat.T, self.incov_tot, self.rgemat
-            )
-
-        self.n_dat = len(oo_wc_basis)
-
-    def compute_chi2(self, coefficient_values):
-        chi2_value = jnp.einsum(
-            "i, ij, j", coefficient_values, self.incov_tot, coefficient_values
-        )
-
-        return chi2_value