â? Replacement filter for pool and spa cleaning systemsâ? 50% open ABS free flow cores maximize water flow through REEMAY filter mediaâ? Antimicrobial end caps resist chlorine degradation and provide support to filter material for a longer life spanâ? Length 23 1/4" Outer Diameter 8 15/16" Top Hole & Bottom Hole 4"â? Replaces Unicel C-8412 and Filbur FC-1293â? Made in the USA