@mozzarellalaIt is just Standard shader with carbon fiber texture you can find from google, Metallic and Smoothness set to 1, i dont know how good Standard shader looks in VRChat but maybe you can try https://vrcmods.com/item/4039-ReroStandard-A-Standard-shader-hack-for-VRChat for it. Visemes are Unlit.
@mozzarellalaYou can change the materials yourself to whatever you want, i didn't include any in the unity package. Just click the "body" of the mask and drag & drop whatever to mask and visemes material slots.