added faq on headcasts, thanks to @mirandanaaktgeboren

faq.md

@@ -105,6 +105,7 @@ See also the [tutorials](/tutorial) and [example scripts](/example).
 - [Should I use a Polhemus or a Structure Sensor to record electrode positions?](/faq/structuresensor)
 - [What is the conductivity of the brain, CSF, skull and skin tissue?](/faq/what_is_the_conductivity_of_the_brain_csf_skull_and_skin_tissue)
 - [What is the difference between the ACPC, MNI, SPM and TAL coordinate systems?](/faq/acpc)
+- [What material is used for the flexible MEG headcasts?](/faq/headcast)
 - [What kind of volume conduction models are implemented?](/faq/what_kind_of_volume_conduction_models_are_implemented)
 - [Where can I find the dipoli command-line executable?](/faq/where_can_i_find_the_dipoli_command-line_executable)
 - [Where is the anterior commissure?](/faq/anterior_commissure)

faq/headcast.md

@@ -0,0 +1,10 @@
+---
+title: What material is used for the flexible MEG headcasts?
+tags: [faq, meg]
+---
+
+# What material is used for the flexible MEG headcasts?
+
+For some projects at the DCCN we use flexible MEG headcasts  to reduce subject motion and to allow precise repositioning over sessions. The procedure we use is derived from the publication by Sofie S Meyer, Gareth Barnes et al. (2017) [Flexible head-casts for high spatial precision MEG](https://doi.org/10.1016/j.jneumeth.2016.11.009) and is outlined in some detail on <https://github.com/Donders-Institute/meg_headcast>.
+
+The foam we are using is <https://www.smooth-on.com/products/flexfoam-15/>.