Pleatco: PWK40 | Unicel: C-6600 | Filbur: FC-3930 • Diameter: 6 1/4" • Length: 11 11/16" • Top: Open Hole: 3" • Bottom: Open Hole: 3" • Filter Area: 45 sq ft • Filter Material:reemay (3 oz/yard) Alternate Filter Names: 31115 | APCC7529 | FC-3960 | PWK 40 Used in pools / spas made by: Hot Spot Spas | Hot Springs Spas | Watkins Mfg. and other manufacturers