Peterson Fluid Systems Dry Sump Screw-In Breathers are made to screw directly into the breather bung on Peterson Dry Sump Tanks. They can also be used on engine valve covers as a fill plug or breather. A one way check valve option is available. This valve seals engine from air entering engine, but opens in the event of crankcase pressure, allowing crankcase to vent. Includes bung and filter.