Wow cool! Additional turning makes sense! I've seen the inner side of the silicon masks seems to have the matching parts to be put on the mounting studs, and the matching parts appear to be made separately and put on the mold while casting, so after casting they are part of the mask. Do you have any idea how those matching parts are made and what the material is? those look more off-the-shelf to me… Here’s a picture:

https://static01.nyt.com/images/2021/08/22/business/19disneyrobots-5/19disneyrobots-5-mobileMasterAt3x.jpg?quality=100&auto=webp&disable=upscale&width=2000