Superlative Arms uses a smart Bleed Off design to vent extra gas out the front of the block, instead of choking it down like older adjustable gas blocks - giving you smoother operation and less mess. 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 3/4 inches x 1 inches solid set screw QPQ melonite 416 stainless steel piston gas block Left-handed, fully automatic AR-15 bolt carrier, dark DLC coated, 8620 steel Mid-length gas system/operating rod length