It's a 5-stage filter:

1st Stage: NSF Certified 5 micron high-capacity polypropylene sediment filter held in a transparent housing
2nd Stage: NSF Certified GAC Carbon Filter
3rd Stage: NSF Certified CTO Carbon Filter
4th Stage: NSF Certified High Rejection 75GPD TFC reverse osmosis membrane
5th Stage: NSF Certified Total Polishing Inline Carbon