I remember DGW had those listed in their catalogue at one time. It may still be there, I just haven't looked in their catalogue in a while. Dixie has always listed quirky novelty gizmos, and this is no different. The installation was described as simply removing the old nipple and screwing in the primer nipple, so I assume the reverse is true.
Isn't it amazing how people tend to take a simple system and fudge it all up with junk like this? These primer nipples are expensive compared to "real" nipples, primers cost much more than caps, and the whole thing is inherently problematic! K.I.S.S :rotf: Bill