UPDATE February 2023 -- both (the genuine Delta and the generic Ace Hardware are still good. No issues since the replacements with either. I would say that the genuine Delta is smoother due to the rubber and not plastic, so for a few dollars more, I would go with that)
Repair a Leaky Faucet (two handle Delta, most popular being the Delta Delex) by replacing the Seats and Springs.
The genuine replacement part is the: RP4993
Diagram for anyone that finds it helpful: images.homedepot-static.com/catalog/pdfImages/97/97a78420-da34-4d43-a751-7929201c745f.pdf
(Alternative url to diagram: ibb.co/7JpTVSS)
You can find the official and genuine part at Home Depot, Lowe's, Ace Hardware, or Amazon:
* Home Depot for $4.47: www.homedepot.com/p/Delta-Universal-Seats-and-Springs-Repair-Kit-RP4993/100169417
or
* Lowe's for $4.49: www.lowes.com/pd/Delta-Metal-Faucet-Spring-Kit/1060669
or
* Ace Hardware for $6.99: www.acehardware.com/departments/plumbing/faucet-and-faucet-repair/faucet-seats/43086
or
* Amazon for $4.49: www.amazon.com/DELTA-FAUCET-RP4993-Delta-Faucet/dp/B000BQYI9W
Alternatively, if you are ok with using a "3rd party" (non-genuine) replacement, you can use the Ace Hardware version for half the price, which is the: 4202552
* Ace Hardware version for $2.99: www.acehardware.com/departments/plumbing/faucet-and-faucet-repair/faucet-seats/4202552
(NOTE: it seems the Ace Hardware's non-genuine version is plastic and not rubber. Not sure if this is a good thing or a bad thing. I'll test them out.)