We offer genuine Unicel replacement spa and pool filters. This 4 ounce filter has an open top and an open bottom with 158 pleats. It has 2 cartridges per set with a stick handle, and is rated for 50 square feet per set. 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: FOR SUNDANCE SPAS, PART NUMBERS C-4401 AND C-4405 ARE REQUIRED TO REPLACE 6000-134