Spa filter cartridgesClarathon FC-2390 Spa Filter (replaces Pleatco PRB50-IN / Unicel C-4950)
50 sq ft top-load cartridge used in many Rainbow, Waterway and generic spas.

$48.99 + $8.99 shipping
45 sq ft front-access skimmer filter for Waterway equipment.
Hurricane HF6H940-01 Filter (replaces Unicel 6CH-940, Waterway 817-0050). 45 sq ft front-access skimmer filter for Waterway equipment.
A clean, correctly sized cartridge keeps water moving through the heater and jets. Most hot tub flow errors (FLO, FL1, dr, HFL) and many no-heat calls start with a clogged filter. Match the length, diameter and end caps (open hole, threaded or handle) against your old cartridge before you order; the cross-reference numbers below are the quickest way to confirm.
Spa filter cartridges50 sq ft top-load cartridge used in many Rainbow, Waterway and generic spas.
Spa filter cartridges25 sq ft cartridge for smaller spas and skimmer baskets.
Spa filter cartridges65 sq ft filter for Hot Spring and Watkins spas.
Spa filter cartridgesPremium-media version of the common 50 sq ft cartridge.