FIT:(2pack) Cartridge Pool/Spa WATKINS HOT SPRING C6430 UNICEL C-6430 PLEATCO PWK30 FC-3915 Replacement Filter Cartridge for Unicel C-4950-2, Filbur FC-2390 and Pleatco PRB50-IN Replaces Pleatco PRB50-IN Replaces Filbur FC-2390