Roll Over valves work by allowing air into the tank to replace the fuel being used, air out of the tank due to heat expansion and a positive shut off to prevent fuel escape due to the vehicle rolling over. These are made from billet aluminium and anodised to protect it. It hasa ball bearing inside the bottom half that allows the air to breathe easily without any restriction. However, if the tank is turned upside downthe ball bearing drops to the top of the fitting effectivelycutting off the exit. These bolt in roll over valves are designed to install in to a fuel tank or cell as a bulkhead style fitting. Available with -6 to -16 AN fittings and come with 2x Teflon Washers to sealing.