Hi Dee, Thank you for your question!
There are two versions of the 21902 model. If your faucet has a supplier code of 413763 on the back of the escutcheon ( base plate) you will need to order the RP47422 stem unit kit. If your unit has a supplier code of 449401 you will need the RP25513 stem unit kit and RP4993 seats and springs ( washer) kit.
Best regards, Brandis
Date published: 2016-01-27