Replacement water filter cartridges for the Brita FF-100 Faucet Filter Systems, 42201 in white and 42622 in chrome. They are also compatible with the Brita 42633 On Tap Black Chrome Faucet Filtration System. For optimum results change every 4 months or every 100 gallons, approximately. This will maintain taste and odor improvement and reduce unwelcome chemicals present in the water. Another choice of Brita faucet filter can be found here.