Lay In Clean Spa Hot Tub S1 Washable Bio Foam 1/6X VI LAZY Filter Fast Shipping Color:BlueYou 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 for around the same price like square or hexagonal. They are this shape because they are cheaply made and obviously not as good fitting as the round types that give a more consistent surface area. These filters do require more attention and I recommend using Bromine as this chemical is odourless, cheaper, better for your skin and much more filter friendlyIf you do choose to use Chlorine i strongly recommend changing these filters weeklyPlease note these filters will lose some colour through use.. This is completely normal and is nothing to panic about. other sellers colour their foam green to hide this, however I believe in being completely transparent with my customers