The Evolution-RO1000 KDF/Catalytic Carbon pre-filter is the standard carbon pre-filter included with system. For chlorine and chloramines reduction for city water. Also reduces iron, hydrogen sulfide and heavy metals in well water. Replace every 2,000 of product water. The Evolution-RO1000 Membrane Element is the standard membrane included with system. Two (2) needed for system. Reduces 94%+ of total dissolved solids. Replace when product water decreases and/or ppm's increase.