Product Information Filtration Size: 10 sq ft Outside diameter: 4 1/4 (10.8cm) Top finish: 2 1/16 (5.2cm) open hole Bottom finish: 2 1/16 (5.2cm) open hole Length: 4″ (10.1cm) Pleatco ref: PWW 10 Unicel ref: C4310 Filbur ref: FC-3077 Great Barrier ref: N/A Our Filters will fit the following Hot tubs PDC Spas Sofspas Thermo Spas Viking Spas Coast Spas Roto Spa Certikin Garden Spas Leisure Bay ref 378900 Please check the measurements before ordering. You are bidding on 1 Filter! Castle Hot Tubs is a well established, trusted name in the water care industry, we will do our very best to ensure that your purchasing experience with us is a pleasant one.