The Bobro Engineering Double-Decker QD rail riser is designed to supplement an existing rail, giving you 5/8" of additional height and two quick detach levers for easy on/off the host firearm. It is very stiff, and the cantilevered end has a tapered reinforcement rib so that it cannot flex even under severe use. The bottom clamp portion uses 10 cross slots on a Mil-Std 1913 Rail with two machined in indexing lugs which enable the riser to return to zero when placed back in the same rail slots. The total length of the riser is 15 rail slots. The base permits the use of back up iron sights on the AR15/M16 series of weapons if desired. It weighs 5 ounces, is constructed from 6061-T6 Aluminum, and uses our proven BLACR technology.