Stupid Bushmaster. That thing is a POF Predator. It isn't easy to install because you have to remove your front site/gas block, flash hider/muzzle break, delta ring, etc. It is a very nice rail system, though, in my opinion. You can get more info on it by looking up the patriot ordinance factory predator p4. I have no idea why all of Bushmaster's accessories are made by YHM or POF now. They have the ARMS SIR in their catalogue; I'm surprised they don’t call it the "BMAS RERF" (Really expensive rail fore end) or something.