The Troy Quick Attach Rail Sections secures with two screws to a backer on the inside of certain Troy Rails. For use on Alpha, Delta, TRX 308, TRX Extreme, Troy HK rails and T-22 Sport Chassis, M7 Uppers and M7 Kit, the Troy Quick Attach Rail sections accommodate a full range of accessories and installing them solidly onto the rail. Features: Black finish 4.2 inches quick attach picatinny rail section Fits certain TROY rail systems Secures with two screws