2 x Hot Tub Spa Filter Compatible w/ Pleatco PTL18P4,Unicel 4CH-21,Filbur FC0121
Unicel 4CH-21, PTL18, PDM25P4, PTL18P4, FC-0121, 20245-238, SD-00845. They excel in removing impurities, such as dirt, debris, oils, and contaminants, effectively preventing them from circulating in your spa water.