Amazon.com : Tier1 Pool & Spa Filter Cartridge | Replacement for Watkins 31489, Filbur FC-3915, Unicel C-6330, C-6430, Pleatco PWK30, SD-00328 and More | 30 sq ft Pleated Fabric Filter Media :
31489 (Antimicrobial) Replacement Filter Cartridge with 1 Filter Wash
Watkins 31489 Spa Filter Cartridge Replacement
Yoozell PWK30-EC Spa Filter Cartridge Replaces for C-6430,FC-3915, CCP498, 13004, AK-5005, XLS-602, FC-3915M, Hot Springs 31489, Darlly 60307, 30 sq.ft Drop in Hot Tub Filter-4 Pack - Yahoo Shopping
Tier1 10.5-in x 5.88-in dia 31489 30-sq ft Pool Cartridge Filter 5-Pack in the Pool Cartridge Filters department at Lowes.com
31489 Replacement Filter Cartridge with 3 Filter Washes