A small white cylinder to add to the puppet arms and puppet torso to assist in the threading of puppet arms into the torso.  See my blog post on how this is used.  It's sewn into the top of the puppet arm along with a knotted shoelace and glued into the puppet torso to assist the lace threaded into a torso and secured with a cord stop.  See my blog post here for directions for use.  https://www.liveactionpuppets.com/the-best-way-to-add-a-shirt-to-your-puppet-removable-arms/

I print my hardware in ABS or ASA, but any filament will do.