100% Brand New and High Quality Color: Blue Quantity: 4pcs You are looking at Z-type foam filters that are compatible with many models of inflatable hot tubs. Be warned, you will see many misshapen versions of these filters for about the same price as square or hexagonal ones. They are this shape because they are cheaply made and obviously not as good as the round types which provide a more consistent surface. They are also unusually thick which obviously restricts water flow which puts a strain on your pump. Why put a thick hexagonal piece of foam in a housing designed for round filters? I myself used the original filters for about 12 months and noticed that they only lasted about a week. They were almost impossible to clean. More importantly they cost me a fortune. I decided to look into a foam alternative and after about 6 months of trial and error I settled on the filters you can see in this list. I have been using them since then with no problems at all. These are much cheaper than the original filters, much more free flowing and I find they filter much better. I have managed to buy round filters instead of the cheaper misshapen ones sold elsewhere. These filter the water much better due to the consistent surface and have proven to be a better fit. These filters require more attention and I recommend using bromine as this chemical is odorless, cheaper, better for your skin and much more filter friendly. If you choose to use chlorine I highly recommend changing these filters weekly. Please note that these filters will lose some color with use. This is completely normal and nothing to worry about. Other sellers dye their foam green to hide this, but I believe in being completely transparent with my customers.