The patent pending SMOOTHCAM system features a domed head, low friction cam pin and special upper receiver that offer ultra smooth operation. With its blended cam recess the UAR upper is machined from Billet 7075-T6 certified aluminum and milspec, Type3, Class2, Deep Black, Hardcoat Anodized. The UAR is a precision machined upper with a special burnished bore that gives a compacted internal surface with a roughness average in micro inches of 16, as opposed to standard bored or milled uppers that are 32-63, or higher. This reduces bolt carrier friction and creates a much smoother operation. Barrel nut threads, bore and barrel extension surfaces are all machined in one operation so that they are perfectly concentric and perpendicular to the barrel and fixing assembly. The cam pin recess has been carefully designed with a smooth surface that flows into the main reciprocation channel. This allows our specially designed radial, domed head cam pin to move with the minimum of wear against these internal surfaces. The CP-R360 Cam Pin has no moving parts to break or lock up. Machined from 17-4 PH Stainless Steel and hardened to H900 (45RC Approx) its head is polished for a super smooth finish. The cam pins circular head has a single flat face machined into it at the front so that it can be inserted into any bolt carrier without having to remove the gas key. Two further flats are machined at 90 degrees to the front face that assist in reducing internal wear to the cam channel. The unique domed head allows the cam pin to operate in a completely different position to a traditional pin, with the radius of the head curving away from the receivers internal surface, rather than forming a hard or sharp edge on its upper corner that causes wear. Finished in its natural hardened state, copper/brass color. Used in conjunction with our UAR upper and you have a complete, ultra smooth, low friction, minimum wear system. ITAR Notice: This product is made in specialized factories by LANTAC USA LLC for sale within the USA only. Lantac UAR Billet Upper Receiver LA00221