These 2.5 gallon gas tanks are top quality, nice thick steel with a center mount American style filler bung that accepts stock style screw in filler cap. Single 13/16" petcock fitting, and a vent tube that is soldered shut.

To run the vent tube just melt the solder out, though the gas cap bung is set up for a vented cap anyway. Take a look at the first two photos below for the dimensions on this tank.