This replacement filter cartridge replaces Unicel # C-5345, Pleatco # PLBS50, Filbur # FC-2970 and OEM # R173584 as other specifications. It can bear the top load of 45 sq. ft. and is best fit for Rec Warehouse S2/G2 Spa, Leisure Bay Spas, Waterway Plastics, Pentair Pool Products-Rainbow Pl, Dynasty Spas, Garden Leisure, Rocky Mountain Spas. Very easy to install this filter cartridge has 2 1/8 inch hole both at the top as well as bottom. It is a great quality filter cartridge that gets installed easily.