I prefer to use Spring Air retracts as they are spring loaded down, which means you will not have a wheels up landing if you loose air pressure. If you use Spring Air, order the set with the 3/16 inch strut wires as the 5/32 have a tendeancy to bend. The plumbing is a single air line to each retract unit that feeds back to the control valve and then from the control valve to the fill valve and air tank. It is really quite easy. Good Luck, Dave