These little doo-dads are press fitted inside the metal bridge thimbles to help stabilize movement of the bridge. I measured .513" diameter on the upper lip, .314" diameter on the portion that goes into the body, .317" length overall, .261" inside diameter of the hole through the center. Looks like semi translucent white nylon to me. Also fits the thimbles and posts found or USA VIntage/Original Jags and Jazzmasters. If you're offsetting on a budget I'm very happy to report that these thimble sleeves also fit exactly the 'Generic' Jag./Jazzmaster threaded saddle bridge we sell as well as our 'Generic' Mustang and 'Generic' Cobain style bridges. These came from Fender as raw parts so no packaging. Set of 2.