The PUR RF-9999 Faucet Water Filters (3-Pack) replace the PUR RF-4050 faucet filter, PUR RF-3375 faucet filter, and the PUR RF-3050 faucet filter. It fits all the PUR faucet filter systems. The PUR RF-9999 replacement filter can be used on the horizontal styles, vertical styles, Plus faucet systems, Ultimate faucet systems, and Delta Simply PUR faucet systems. The device is tested and certified by NSF International to meet or exceed NSF/ANSI Standards 42 & 53. The PUR RF-9999 Faucet Water Filters (3-Pack) reduces Lead, Asbestos, Benzene, MTBE, and TTHMs. The activated carbon filter removes 99.99% of the Microbial Cysts Cryptosporidium and Giardia. The water filter has added layer to trap sediment. The PUR RF-9999 water filter cartridge is quick and easy to replace. Replace the PUR RF-9999 faucet water filter cartridge every 2-3 months or every 100 gallons of water depending on your water quality and water usage. Before the first filter use, flush the filter by running cold water through it for 5 minutes. Before each filter use, run cold water through it for 5 seconds to activate the filter. The filter should be used with cold water only. PUR FM-1300 Faucet Water Filter System, PUR FM-3000 Faucet Water Filter System, PUR FM-3333 Faucet Water Filter System, PUR FM-3350 Faucet Water Filter System, PUR FM-3400 Faucet Water Filter System, PUR FM-3500 Faucet Water Filter System, PUR FM-3550 Faucet Water Filter System, PUR FM-3600 Faucet Water Filter System, PUR FM-3700 Faucet Water Filter System etc are the models that can use the PUR RF-9999 water filter.