The 3H series is pretty old. I had a faucet from the early 2000s, and it finally started leaking. I replaced one stem/cartridge. Then, a year later, the other one started leaking.
These lasted a long time, so I didn’t mind paying so much for a replacement ($13 or so), but it seemed to me like the rubber parts should be replaceable.
Replacing the entire cartridge seemed so wasteful. Well, I was correct – you can replace just the washer – and I was also ignorant, not having checked the part references.
I also already gave away the first cartridge, basically giving away a $18 item for free. Oh well.
Note that I called it a cartridge. It’s really more like a stem. It looks like a cartridge, but it’s not.
The washer is called a “bottom seal”. I didn’t know.
The valve was from the 3H-8 series. They have names like 3H-8C, 3H-8HC. Some are hot and cold, some are cold only.
The specific part I needed was the Danco 80359 1/4″ Faucet Seat Washers for Price Pfister. They’re widely available online.
At $5 they aren’t cheap, but, they are cheaper than buying a new cartridge. The design of the system reduces wear on the washer, so it lasts a long time.
Video about this: https://www.youtube.com/watch?v=otnYaKpwrjU