Before they were available from the club, TT uploaded a PDF on this forum with dimensions so I could make one for myself as my Shadow with MK II cams had eaten the guide for lunch and spit out the remnants down the exhaust pipe. The ensuing carnage had also destroyed the lock ring and threads in the head. Being fortunate enough to have both a vertical mill and lathe it was easy enough to make and works quite well. In retrospect I only regret not making and fitting them to the other 3 valves whose lock rings were still good, as a safe guard for the lock rings on those valves coming loose. While I like the idea of the lock rings for retaining the lower valve guides, I don't understand why something like the WW wasn't used in the first place. It is far easier to make than cutting a thread down valve guide tunnel and easier to fit than a lock ring down the same tunnel. Add to that in the absence of Loctite one has to resort to punch locking the ring, which has its own issues when trying to replace lower valve guides. I have already decided when I turn my attention to my Comet's engine, it is getting two, even if the lock rings are good.
Steven