Superlative Arms' AR-15 piston system uses a unique bleed-off design that vents extra gas out the front, instead of simply blocking it, giving you a smoother, cleaner shooting experience. Gas adjustment (patented) - features 30 fixed positions located at the front of the block Bleed-off port (patented) - located at the front of the block, designed to vent forward, directing emissions away from the operator 0.625 inches x 1 inches solid set screw QPQ melonite 416 stainless steel piston gas block Right hand, full-automatic AR-15 bolt carrier, dark DLC 8620 steel Mid-length gas system/operating rod length