This is a Mako GMG AR15/M4 Carbine Aluminum Quad Rail System. This rail is made from lightweight aircraft aluminum that is fully anodized not painted. It comes in two pieces for easy installation. Unlike many cheaply painted quad rails, the GM-QR1 is fully anodized. GMG has included rail slot markings to enable the user to remove and replace accessories in the same spot. In order to foster quicker cooling, especially under paid fire, these quad rails have four rows of seven holes machined into the sides to increase airflow and heat escape. There are four Mil-Spec Weaver-Picatinny rails for all your mounting needs such as lasers, lights, forend grips, bipods and sights.