Unicel C-4401 | 35 sq ft Spa Filter Cartridge

 The Unicel C-4401 delivers 35 square feet of filtration across 158 pleats of heavyweight 4 oz Reemay® 2040 polyester media. Built to meet or exceed OEM specifications, it's the compact replacement cartridge for Pentair, Rainbow Dynamic Series IV, and Waterway skim filter systems.

Filtration is the quiet backbone of clean spa water. Every soak leaves behind body oils, lotions, hair, and fine debris, and the cartridge is what removes all of it before it clouds the water, feeds bacteria, or coats your plumbing. When a filter is worn or clogged, the effects spread everywhere: dull water, higher chemical use, softer jets, and a pump and heater straining against restricted flow.

What sets this cartridge apart is the heavier media. Where most spa cartridges use a 3 oz fabric, the C-4401 is built with 4 oz Reemay — a denser, more substantial material that stands up better to repeated cleanings and resists the matting that shortens a filter's life. Its trilobal fibers, three-lobed rather than round, deliver roughly 45% more surface area than standard rounded filter fibers, so it captures more while releasing dirt readily when rinsed. Chemical-resistant end caps with open 2-1/8 inch ends make installation straightforward. Made in the USA.