Evolution Series 7-EX The Samson Evolution Series is the next step forward in free floating hand guards. Light weight and durable these offer the perfect upgrade for 3 gun shooters LE/Military or weekend enthusiasts alike. 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. Kit includes: Thermal bushings (2) 2 " rail kits (1) 4 " rail kit instructions & wrenches.Rail Accommodates most piston systems.