Black Rain Ordnance, Inc. Black 7" free float carbine quad rails Constructed of 6061 T6 aircraft grade aluminum, collar is made of 2024 aluminum. Screws are high carbon steel dipped in black zinc which require a tool less installation. Features include blacked out "T-marks", with 100% backwards compatibility, quick detach swivel cup, hard coat type III class 2 black anodizing MIL-A-8625; weighs 9.8 oz. installed. Made in the USA.