New Br High Quality Col:Blue Qty:4pcs You are looking at Z type foam filters that are compatible with many models of inflatable hot tubs. Please be warned, you will see many misshaped versions of these filters f around the same price like square hexagonal. They are this shape becse they are cheaply made obviously not as good fitting as the round types that give a me consistent surface area. they are also unusually thick which obviously restricts water flow putting excessive strain on your pump. Why put a thick hexagonal lump of foam in a housing designed f round filters? I used the iginal filters myself f approx 12 months noticed they only lasted around a week. it was almost impossible to clean them. Me imptantly they were costing me a ftune I decided to look into a foam alternative after about 6 months of trial err I settled on the filters you can see in this listing. I've been using them ever since with no problems at all. These are much cheaper than the iginal filters, much me free flowing I find they filter much better. i have managed to source round filters rather than the cheaper misshaped ones that are f sale elsewhere. these will filter water much better due to the consistent surface area are proven to be a better fit. These filters do require me attention I recommend using Bromine as this chemical is odourless, cheaper, better f your skin much me filter friendly If you do choose to use Chline i strongly recommend changing these filters weekly Please note these filters will lose some colour through use.. This is completely nmal is nothing to panic about. other sellers colour their foam green to hide this, however I believe in being completely transparent with my customers