The Samson Evolution Series features a free-floating 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. Rail accommodates most piston systems. This is the 9"" Carbine Length Evolution Rail for the AR-15.Standard Evolution Series Includes: Thermal bushings"" Two (2) 2"" accessory rail kits"" One (1) 4"" accessory rail kit and wrenches.