Fil-fresh Robotic Pool Cleaner Filter Compatible with Dolphin m400, m500, Nautilus CC Plus, 4-Pack Ultra-Fine Filter Replacement 9991432-R4

I've used these filters for several months now. The ultra-fine filters (like these) that came with the robot didn't do a very good job. It seemed that most of the water went around the filters, not through the filters, taking the fine sediments with it. There is more sediments trapped with these new filters than with the old, so they are doing a much better job. (Note: they still don't catch tons of material, and use the "spring" filters if you see larger pieces of leaves, etc. on the pool bottom.)

I have ordered a few of these replacement filters. The brand i typically order was not available and these were. The filters are strong and fine... they do the job, but they are a much tighter fit than the previous brand. I really have to push / snap them into and force them to come out. It is fine now, but worried over time the plastic will fatigue and break. We'll see.

Almost all of the plastic tabs had broken off of all 4 sides of our original cartridges. This was after 4 years of steady use. I decided to give these a try as they were quite a bit cheaper than the competition. They area a perfect fit in our original frames. no forcing. No gaps that I can see. I'll update if needed after the first cleaning run.

This is great pool cleaner. The filters pick up fine particles such as algae and leave the pool super clean. I highly recommend this pool cleaner.

A must have and game changer for your nautilus cleaner. Gets up sand and small debris. Fits like a glove.