Still, you could have used the O ring that came as part of the regulator. Either way, one becomes an extra. Part of the problem is that Scubapro does not include much in the way of instructions with anything they sell, expecting consumers to seek the technical assistance of a SP dealer for ridiculously simple things like switching from Din to yoke and vice-versa. If you can change and set the points in your VW Beetle's distributor, you can do this as well. Wait, did I just date myself?Actually the universal DIN kit comes with the pre installed wheel retainer O ring and a loose O ring part 01050347 that seals against the regulator body which is small and the loose "extra" O ring that apparently works the way Angelo said. There is also the DIN O ring for the valve preinstalled. It was the loose "extra" O ring that was causing the confusion for me. I didn't use any original yoke O rings