CNC Aluminum Hopup Chamber MI Pro (with BB Latching System) unit is precisely made to improve accuracy and ensure consistent air seal for ICS CXP/CS4/EBB (include old models) M4/M16 AEG series. The Hopup Chamber MI unit has a precision rotary dial design for fine hopup adjustments, also re-engineered the hopup levers and concave nubs to work best ..