It is a R-4 compressor. The old compressor had regular o-rings. The new one has the sandwich seals. The hose manifold has the stepped ports. The discharge side had a pilot tube coming out of it whils the suction side is flat. The instrutions fail to talk about this configuration. I installed it according to the guy who sold it to me, and it leaked out in a day. We did a leak test and it is leaking from that seal ( the discharge side). Is is true that you have to use the short sleeve ( that comes along with the R-4 compressor) in conjuction whih the green seal? That's how it's desribed in the shop formum's online catalog.