SPECS: Machined 6061 T6 billet aluminum, hardcoat anodized, matte black. 7” (17.8cm) long, 2½” (6.4cm) diameter. Fits AR-15/M16/M4 and clones with carbine-length gas piston operating system and ½” diameter gas cylinder. Mounts over existing factory barrel nut without removing front sight base. Requires removal of Delta ring.