Armalite 308 Gen III Free float Forearm Rifle Length is 15.75". The latest PRi Gen III free float forearm Rifle length are constructed of light weight high strength carbon fiber, aluminum and high strength steel for the best possible combination of weight and strength. The carbon fiber also reduces the amount of heat transferred to the shooters hand during rapid or high volume firing. The forearm comes with 4 rails a 8.5" rail on top and (3) 3" rails at 3,6, and 9 O'clock positions. Available in Natural, Flat Dark Earth and Black.  Forearm weights 1.17 Lbs. with standard rail configuration.  ID of the tube is 1.9 inches.  Tools to install forearm not included.