Different valves were used for the r-12 and 134 refridgerants. I think the 134's are larger, but you can compare to the kits at the auto stores, or just take it to a shop and they will be able to tell you. Any caps on the valves? If so, what color? My 134 kit came with a blue cap for the low side which I put on after screwing the adapter valve on the original valve. Make sense?