We are working to make our website better. We want to allow you to be able to search and find the items you need quicker. We are striving to make the searches easier. We have been using this formula to allow you to search for the replacement cartridge filters for you hot tub. You can now search by any manufacturer’s numbers (i.e. Unical, Filbur, Pleatco, etc.) Put the number in the search box and search. You can search all filter cartridges by the manufacturer of your spa. Put in the name of the spa (i.e. Coleman), do not press enter but wait for the suggestion list to come up and then choose your spa name. It will take you to the filters that fit that manufacturers spas. Just choose yours. You can also use this method to use the diameter of your filter (i.e. 8-1/2”) Type in the size, wait for the suggestion list and choose the size. When the page comes up with the cartridges of that diameter, choose your filter. If you can not find your filter or if you need help, please contact us at [email protected] Let us know how we can make our site better for your use. We appreciate any constructive criticism you may have.