These are not listed on any of the exploded drawings for any snare drums, but they are used on several of the German made metal shell snare drums. The Asian made snare drums use the metal cups.
What a fiasco I had with finding these. SamIam studios had the picture of these parts on eBay and I bought them. USPS lost the package, so he had some drop shipped to me, and they were the flat ones used to insulate the outside of the shell from the lugs itself. Finally, got it figured out and I am posting this here for the benefit of anyone needing these parts as well as for my own future reference.