This rollover valve bolts directly to the fuel cell bladder with a 6-bolt flange. Requires a 1 1/4" hole in the bladder and 2 3/4" of clearance in the plate. Nut ring and gasket are included, but we also offer a replacement Round Gasket with 6 x 2" Bolt Circle (Part No. FS 1GAS76). Accepts 1" ID vent hose. This valve is not spring loaded. It depends on gravity to close the valve in the event of a rollover.