Maxx Model CNC Aluminum Hopup Chamber M4A-Pro (with BB Latching System) unit is precisely machined to perform accurately and consistently with Tokyo Marui-spec M4 V2 AEGs (not compatible with most or all KWA). Designed for AEGs and HPA engines (excluding Polarstar) Check out my other listings! Everything ships the same or next day, to your door in 2-4 days!