Looking around for gas rings I found another vendor that had 15 for $6 - what a deal! Except that of the two ratings, one reviewer said that the rings from that vendor made it so the bolt wouldn't fit in the BGC. Just get BCM stuff. The saved pennies are not worth the hassle. Everything from BCM works, and works well. Prices are pretty good too, but even on items where they're a bit higher, the savings in frustration and aggravation would make BCM stuff worth it at 2x the price.
Everything they supply is quality. If you're not happy, they're not happy. They will go out of their way to make sure your satisfied. Don't buy AR15 stuff anywhere else. Customer service is second to none!!!!!!!!!!!!!