Perfect Fit: Compatible with faucet water filter systems (classic, advanced, vertical & horizontal), including FM3700, PFM400H, PFM350V, PFM100B, FM4000B, PFM450S and more. Replace filter# RF-3375. All manufacturers' names and part numbers are used for compatibility information only Save Your Bills: 3 Packs work as well as the original filters, but at a lower cost. Filter up to 100 gallons of water or replace it every 3 months Powerful Filtration: Certified activated carbon and ion exchange system reduces 99% of lead, chlorine, rust, sediment, etc (over 70 impurities). Greatly remove the bad taste and odor Fast Filter Process: Advanced structure passes through the water smoothly, which ensures stable and continuous clean water flow Easy to Replace: No tools needed. Unscrew the top cap to get out the old filter and insert the new one into the faucet mount until it clicks, then tighten the cap