Madbull Ultimate 3-in-1 Hop Up Chamber Unit for M4 / M16 Series (Free Shark Hop Bucking)

Another practical innovation from MADBULL, this new metal hop-up unit / chamber has 3 functions in 1! Can accommodate internal LED unit for tracer function, chamber lock function to prevent BBs from falling out during reloads, and a new adjustment design that stays in place and won't shift during full auto fire.