Outer Diameter: 4 15/16" Length: 13 1/2" Top Style: Closed Handle; Bottom Style: 2" Female SAE Threaded; Media: 50 SF Compatible with Cal Spa FIL50-5D13H15FCT FIL11100208 Pleatco PWW50L PWW50L-M Unicel 4CH-949 Filbur FC-0172 FC0172M Waterway 817-4050 Baleen AK-90091 Pure N Clean PC-0172 Hot Tub Spa Filter. SpiroPure pool and spa filter cartridges offer long-lasting, durable filter media with high dirt holding capacity for clear, sparkling water in your pool or hot tub spa. A strong inner core means increased strength without hindering water flow or filtration performance. Easy to install, durable filter cartridges that allow for high filtration performance and efficiency SpiroPure SP-PS-0172 Hottub Spa Pool Filter Replacement Cartridge. Easy to install, durable filter cartridges that allow for high filtration performance and efficiency.