CNC Aluminum Hopup Chamber ME Pro (with BB Latching System) unit is precisely made to improve accuracy and ensure consistent air seal for Tokyo Marui (include KRYTAC, except KWA) M4/M16 Standard AEG series. 
The Hopup Chamber ME unit has a precision rotary dial design for fine hopup adjustments, also re-engineered the hopup levers and concave nubs to work best with R-hop and Standard-Hop to keep the BBs shooting straight and accurate on every single shot. 
The Hopup Chamber ME unit is designed to accept the nozzle length from 21.00mm to 21.25mm, and fully compatible with most aftermarket soft and hard rubber bucking without losing FPS or dropping BBs. 
The Hopup Chamber ME Housing is equipped with a new CNC Delrin Locking C-Clip design to hold barrel tight without wobbling and twisting, and 3 compression springs on top, at bottom and in center of housing to ensure the hopup unit is exactly centered, straight and air tight at all times when adapted to any V2 gear boxes with 11mm or 11.5mm inner bore. 
More than that, the Hopup Chamber ME Pro unit is specially designed with BB Latching System to prevent dropping BBs after removing the magazine. The Latching System can be also manually opened to release BBs from inside hopup chamber by hand.