Autococker Trilogy Competititon, Richoshet AK Hopper, Lucky 15 Barrel set.
Not very many
I was excited about this product at first, but after using it I found it did not really work with any of the guys that were using it on my team. Even the best result we could get was not adequate. I like the concept but it is a poor execution. I finally quit using it during our game and was told the only one who came in clear was me through the mic on the radio. I think the trade off of having no background noise is not a good enough reason to purchase these, I would rather have a little noise and be able to understand what is being said.
Don't bother, get the cheapy mic's at Radio Shack with the ear piece and PTT button. You'll have the same results.