The Pleatco Replacement for Spa Filter PWW50P3 is a high-quality filter cartridge suitable for hot tubs, above ground pools, and in ground pools. Made of Trilobal Filtration Fabric, this filter has a material area of 50 sq.ft and a bottom opening of 1 1/2" sea thread. With an outside diameter of 6 inches and a length of 7 5/8 inches, this filter is compatible with Unicel 6CH-940 and 817-005 models. Easy to install, clean, and salt water compatible, this filter is backed by a 6-month manufacturer warranty and comes in a convenient unit quantity of 2.