Maxx Models CNC Aluminum Hopup Chamber M4A - PRO Product Description   CNC Aluminum Hopup Chamber M4A Pro (with BB Latching System) unit is precisely machined to perform accurately and consistently on Tokyo Marui (include G&G, KRYTAC, except KWA) Standard M4/M16 AEG series.The Hopup Chamber M4A unit is built with an aluminum Rotary Dial Knob...