Can anyone tell me the origin of the fitting used to connect the cu fuel line to the fuel tap and carb as used on a Lister D but also quite common on prewar machinery. The joint has a 1/4 nipple with a shallow cone seat (something like 25deg). This is soldered onto the 1/4 cu tube and the whole lot is clamped with a 1/4 bsp nut. Its a common fitting which i guess we all take for granted (till you havent got one). Where does it come from, whats it called, whats the design standard?