We offer genuine Unicel replacement spa and pool filters. This 3 ounce top load filter has a semi-circular handle top and a 1-1/2" male threaded fitting bottom with 158 pleats. It is rated for 25 square feet. The Unicel spa filter cartridge should be inspected monthly and replaced every six to eight months if the spa is maintained properly. For additional savings, we offer this product in a 3-Pack. (See listing at bottom of this page.) Note: This cartridge can also be used to replace 7" diameter cartridges.