Precision Reflex Free Float Forearm No Rails Gen 3 15in Carbon Fiber Black. Total length of the forearm is 15.5in. 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. Specifications for Precision Reflex Free Float Forearm w/ No Rails: Manufacturer: Precision Reflex Fabric/Material: Carbon Fiber/Aluminum/Steel Gun Make: AR Platform Gun Model: M16 AR-15 Gun Type: Rifle Handguard Length: 15 in Handguard Type: Free-Float Gun Rail: Standard Inner Diameter: 1.75 in Mount Type: Rail Model Generation: 3 Quantity: 1 Package Contents: Precision Reflex Free Float Forearm w/ No Rails Precision Reflex 05-073-15THB: Free Float Forearm No Rails Gen 3 15in Carbon Fiber Black