The Samson Evolution Series is a free-floating modular AR-15 rail system. Being lightweight and durable allows the Samson Evolution Series to offer the perfect upgrade for 3-Gun competition shooting” law enforcement and military personnel or weekend enthusiasts. Accessory picatinny rails can be added or removed at any of 7 positions around the rail and any place along the length of the tube. This rail accommodates most piston systems. Includes: Thermal bushings” Two (2) 2″ accessory rail kits” One (1) 4″ accessory rail kit and wrenches.