HydroLogic PreEvolution High Capacity Pre-Filter ensures your Evolution RO1000 runs more efficiently. Protect the RO membranes and extend their life. Less filter changes and maintenance - every 7,500 gallons of purified water. Cleanable sediment filter is re-usable. Combination of KDF85 and the KDF55 with eco-friendly catalytic carbon filter reduces chlorine, chloramines, iron, sulfur, and heavy metals. - great for city or well water. Highly recommended when using more than 150 gallons of purified water per week on average.