Guardian Spa Filter Replaces Unicel C-4401RA, Pleatco PRB17.5SF, Filbur FC-2386M Antimicrobial Replaces Unicel C-4401, Filbur FC-2386, Pleatco PRB17.5SF Length: 4-5/8", Diameter: 5", Top opening: 2-1/8", Bottom opening: 2-3/16" 35 sq. ft. of Reemay Filtration Fabric infused with Microban antimicrobial product protection Antimicrobial end caps