Select your Challenger water filtration system or Challenger water filter below to find comparable replacement filters. Email support@waterfilters.net if you cannot find your Challenger water filtration system or Challenger Water International Inc water filters. Use these filters in the Challenger Conqueror III & Gladiator III 5 Stage RO System, Conqueror II & Gladiator II 4 Stage RO System, and Conqueror & Gladiator 3 Stage RO system.