The Patriot Ordinance Factory patented Roller Cam Pin is just one more example of how far ingenuity will go to reduce friction and drag. Standard AR cam pins feature a square (steel) head that grinds along the inside of the aluminum receiver. Roller Cam Pin with modified Gas Key for direct impingement-type rifles. Other carrier and bolt assembly parts not included. Used as a replacement part for POF piston Bolt Carrier Groups. For the best selection of Modern Sporting Rifle parts and accessories, shop Palmetto State Armory!