My PP faucet part 533-50*, the white version has been leaking from the base for a long time and never really noticed it until I noticed water and some wood damage showed up under the sink. Wish I had changed it earlier. As a matter of fact, I never changed it when I bought my new home 21 years ago. Its the original. The cartridge part# in the manual calls for part 974-570. But that is no longer being offer from Price Pfister. It calls for a replacement part 974-035 that you can find on Amazon(bought it just in case and will return it). It probably works but I'd prefer a part that is identical(as much as possible). This part fits just fine and after several days of observation, still no leak, and operate smoothly. Only time will tell how durable it is. I also replaced the nylon nut with a bronze nut that secure the cartridge. BTW, the black gasket(surprise its thick not flimsy rubber, should provide a good seal) at the bottom comes with it so no need to buy part #950-100 as shown in manual.