Make your KWA gas M4 even better with the NEW Maple Leaf 6.01mm stainless steel and hop up set! The set does NOT include a bucking. The stainless steel hop up set replaces part #14 in your KWA rifle and provides vastly improved durability and hop up control over the stock hop up unit. Works with all KWA and PTS gas blowback M4s. 260mm length is suitable for the CQB length (10") versions of the KWA and PTS gas blowback rifles.