Vented steel design changes cycle time by letting you adjust the gas volume in the cylinder. Quick adjustment of vent size with integral set-screw; eliminates changing screws for different vent sizes. Reduces battering on op rod, bolt lugs, receiver and trigger group. Available for M1 Garand and M1A. Mfg: Schuster SPECS: Steel, parkerized finish. Replaces existing gas nut with no modifications to the rifle. Includes adjustment tool and instructions.