I've personally used the older STX version and still have it. I've also "tested" it out on 2 occasions and feel that it made a vast improvement over not using one. I know a lot of the local CMRA races in Texas are using them. A few have the orignial STX, with may having the the STX RR version. Looks to me like it is more low profile and lighter weight than the original. The only time I won't wear it is if I'm out instructing and taking it easy. Every other time it is on and ready to go. If you want more info I can point you to a couple racers that I know currently use them.