Features: ● For GHK 553 GBB Rifle only. ● MIL-STD-1913 rail specifications. ● Contains CNC process tactical front-end,551 type length steel barrel, 551 type steel muzzle brake, steel gas tube, and 345mm inner barrel. ● Installation requires replacement of the original 553 type barrel and gas tube. ●《ACTION! REALISTIC SPECIAL CUSTOM》Realistic full laser engraving version.