Shaft Collar Material Question

A buddy wants me to make him an extension to go between the forearm and shaft. I thought I would add a collar/ring on each end to dress it up. Can you tell me what material is typically used for the black collars on most shafts?

Can black delrin be used?

Are the collars just glued in, or are they typically threaded and glued? I'm only planning to make them 1/4" deep, so more like a thick ring.

Thanks, I forgot that glue doesn't stick well to delrin.

Ok, I see Atlas carries Black Linen Micarta, Juma, and Black PVC rods in 7/8" or 1" rods. The Black PVC is the cheapest. I'm assuming glue will stick to it since they have it listed under Ferrules. Do you think PVC work well for my application? I

Thanks for the suggestions! JC was nice enough to to cut and send me a few rings. Great AZB member and builds beautiful cues!