This is a LWRC free-float quad rail for AR-15 platforms, the color is black. This rail in made out of anodized aluminum. This rail will fit standard mil-spec AR-15 pattern upper receivers.
MkII-B ARM-R Rail Assembly - Carbine
The ARM-R carbine Length Rail Kit. This three piece rail kit is made from 6065 series aluminum that is Type III mil-spec hardcoat anodized. The kit consists of three main pieces: 1) Lower section that contains the 3, 6, and 9 o'clock rails, 2) The rail clamp that attaches the system to the upper receiver, and 3)The removable top rail, which attaches to the lower section via hardened steel pins and 'J' shaped cuts that are found on the rail. These hooks and pins allow a 100% return to zero when removing and replacing the top rail. The top rail is held in place by pusher screws, which seat against special high-temp rubber o-rings.
The removable top rail allows the user easy access to the piston components on a piston operated gun or to the gas tube on a direct impingement gun. The top rail can be removed and replaced without tools other than the rim of a cartridge case. This rail kit fits any standard mil-spec upper receiver without any special mounting hardware.
Two Quick Detach swivel mounts (one fore and one aft on both 3 and 9 o'clock positions) accommodate most Uncle Mike's® pattern QD sling swivels. This lightweight and durable rail system has made LWRC rifles and carbine the go-to choice for the operator that needs plenty of 1913 Picatinny mounting surfaces for optics, lights, bipods, and lasers. (Source: https://www.lwrci.com/p-152-mkii-b-arm-r-rail-assembly-carbine.aspx)
