The Samson Evolution EX Series is the next step forward in free-floating handguards. Being lightweight and durable allows the Samson Evolution EX 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 7"" Evolution EX Evolution Rail for the AR-15. Inside diameter fits most suppressors (1.56"").Includes: Thermal bushings"" Two (2) 2"" accessory rail kits"" One (1) 4"" accessory rail kit and wrenches.