Nissan Patrol GQ Genuine Clutch Master CylinderGenuine Nissan Clutch Master Cylinder Suit ALL GQ Models With Boost assisted clutch The vacuum booster is a round black Cylinder that looks like the brake booster only smaller, and it is fitted between the master cylinder and the firewall. if your master cylinder is bolted directly to your firewall then your system is not boost assisted. All of these cylinders have an Aluminium bore, which means they wear easier than a cast Steel bore, hence we have