Sinclair's sells them. They are made out of a nylon type material. The kit consists of 3 brushes: a chamber brush, an upper receiver brush, and a BOLT CARRIER BRUSH! I've seen the first 2 before obviously, but the bolt carrier brush is interesting. The AR15 and AR10 are seperate kits, but the carrier brushes are designed to fit inside the area where the bolt goes AND have a tapered portion that fits into the hole where the firing pin comes through. I have yet to use them (I ordered one of each) but I'm sure it will make cleaning the bolt carrier much easier, especially those hard-to-reach areas.