5 Stage cartridge filter: 1st Stage 10” Pre-filter Spun PP 5 Micron (PT Series Filter) 2nd Stage 10” GAC Carbon (PT Series Filter) 3rd Stage 10” Sediment Spun PP 1 Micron (PT Series Filter) 4th Stage RO Membrane: 50/75/100 GPD 5th Stage In-line Post Carbon Filter