Precision Reflex Gen 3 AR-15/M16 Free Float Carbon Fiber Extended Forearm 15 in Natural. The forearm comes with 4 rails 1 8.5in rail on top and 3- 3in rails at 36 and 9 O'clock postions. The forearm is constructed of wrapped carbon fiber with an aluminum barrel nut and collar. Total length of the forearm is 14.5in and weights 16.6oz. including barrel nut. The clearance from the center line of the barrel to the underside of the forearm is .78in. The inner diameter of the barrel nut is 1.075in Custom barrel nuts with larger ID for larger diameter barrels can be made. Forearm wrench not included. Specifications for Precision Reflex AR-15/M16 Free Float Carbon Fiber Extended Forearm: Manufacturer: Precision Reflex Color: Natural Finish: Cerakote Fabric/Material: Carbon Fiber Aluminum Gun Make: AR Platform Gun Model: M16 AR-15 Gun Type: Rifle Handguard Type: Free-Float Gun Rail: Picatinny Weight: 16.6 oz Mount Type: Rail Quantity: 1 Package Contents: Precision Reflex AR-15/M16 Free Float Carbon Fiber Extended Forearm Precision Reflex 05-073-15: Gen 3 AR-15/M16 Free Float Carbon Fiber Extended Forearm 15 in Natural