The return valve can be assembled into e.g. fuel hoses to avoid the running back of the fuel. Together with a mounted mesh it is called foot valve. For the transfer of plant oil, fueld, etc such an foot valve is required.
Due to the two male threads it is possible to assemble elbow fittings, ball valves and much more. For screwed fastenings both for water and for fuel we recommend the thread seal p-85175 or the thread sealing agent p-97216.
As fuel hose in 1/2 inch we recommend the low pressure hydraulic hose s-kr-12.