The Airtronics Z , JR and Hitec S (sometimes referred to as universal) plugs are totally compatable in wiring polarity and mechanically (plugs fit each other). The Futaba J is the only odd man out The wiring polarity is compatable with the other three however the male J's will not fit the female S, JR or Z unless unless that single flange is removed with a #11 blade and shaved down a bit.

John