Quote Originally Posted by Geezer View Post
The original set up was a PTFE washer backed with a neoprene ring.

I believe later aftermarket replacements are polyurethane. See reference in the Knibbs ad:

http://www.airgunspares.com/store/pr...-Part-No.-V10/
Webley also made their own polyurethane seal for the latest Vulcans and the other guns with the same cylinder diameter. These are purple, but look similar to the Knibbs seal. Jim Maccari and That Australian guy also make aftermakret seals for these guns.