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. No reserve. Length measured without hose barb and filter.