The functionality of this air filter is five stars easily and that is by far the most important metric for my rating from me. There are two significant negatives which is why it only gets four stars. First there is no mounting hardware so you will have to fabricate your own mount or just lay it down. Second the filter cartridges are very expensive. All in all though I use this for the air supply to my CNC plasma table and it does a great job providing clean and most importantly dry air so it still gets four stars.
Rating: [4 of 5 Stars!]