Nobody seems to know much about these things. I have heard that you are supposed to have one dry and shake it next to your ear and if it rattles, it's good. That seems imprecise. I built a jig to test them but discovered there is so much slop on the 2 or 3 threads mounting the OPRV to the case that oil flows past the threads quite easily. I don't think anyone knows how many shims to put in, I've seen none and up to 4. Who knows. I bought a new one from SRM and crossed my fingers. They swear they have been tested but who knows. I also put a gauge on the bike. 40 PSI cold.