Precision Reflex DPMS 308 Delta Forearm 15in Flat Dark Earth. They use a steel barrel nut that is included. The overall length of forearm is 14.75" and weights 1.245 Lbs. Forearms are Cerakoted either Black or Flat Dark Earth. From barrl center to the underside of the forearm is 1.14" and the max ID is 1.40" Bore centerline to top of rail on forearm is 1.328". Specifications for Precision Reflex DPMS Delta Forearm: Manufacturer: Precision Reflex Fabric/Material: Carbon Fiber/Aluminum/Steel Gun Make: DPMS Gun Type: Rifle Gun Rail: Standard Condition: New Mount Type: Rail Quantity: 1 Package Contents: Precision Reflex DPMS Delta Forearm Precision Reflex 03-071-1415DE: DPMS 308 Delta Forearm 15in Flat Dark Earth