The patented Roller Cam Pin is another example of how far POF-USA will go to reduce friction and drag. Standard AR cam pins feature a square head that grinds along the inside of the aluminum receiver. The nickel-plated roller, on POF-USA's cam pin, smoothly rolls along the receiver without gouging the receiver. As a result, you will never worry about cam slot wear again. The Roller Cam Pin Upgrade Kit comes complete with a Chrome plated notched gas key for use with Mil-Spec direct impingement AR-15 bolt carrier groups. Note: This kit is intended for use with Mil-spec AR-15 bolt carriers.