Wolverine Airsoft talks about FRAC to standard gripline with their MTW series... "The FRAC (Fixed Rear Airline Connector) is standard on some MTW like the MTW-308 and the Gen-12 MTW Shotgun. If you prefer another option like the WRAITH or a standard grip line, the FRAC uninstalls as easily as it installs. Sam shows you how on this episode of What the Tech!"