SPECS: 6061 T6 aluminum, mil-spec hardcoat anodized, matte black. Carbine – 7¼" (23.5cm) OAL, 2½" (6.4cm) dia. 12.5 oz. (354g) weight. Fits AR-15/M16 with carbine-length gas system. Mid-Length – 9¼" (23.5cm) OAL, 2½" dia. 15.2 oz. (431g) wt. Fits AR-15/M16 with mid-length gas system. Specter – 9¾" (24.8cm) OAL, 2½" dia. 16.1 oz. (456g) wt. Fits AR-15/M16 with carbine-length gas system and covers gas block when installed. Rifle – 12½" (31.8cm) OAL, 2½" dia. 16.6 oz. (471g) wt. Fits AR-15/M16 with rifle-length gas system.