These small petcocks fit direct to either a 1/4" or 3/8" NPT bung on your gas tank. This keeps your gas tank looking very clean. They feature a 5/16" diameter hose barb on one end and a fuel filter on the other. The manufacturer recommends 1/4" ID fuel line for a snug, leak proof fit. Rotating the cylindrical piece with the two grooves is how the fuel is toggled on and off. The fuel line will not rotate while toggling the fuel on/off. No reserve. Length measured without hose barb and filter.