My 20-year-old hot tub broke :( beyond reasonable repair right after purchasing these new filter cartridges, and do not see another hot tub in the foreseeable future. This Guardian brand of filters has been used the life of the tub, kept the water crystal clear, easy to install and easy to clean. They lasted about 2 years with maintenance amid frequent hot tub usage.

These filters are compatible with Unicel 4CH-24, Filbur FC-0131 and Pleatco PGS25P4. They measure 9-3/4 inches in length and have a diameter of 4-5/8 inches. There is a top handle and are bottom threaded 1-1/2 inch MPT (male pipe thread). They are new in their packaging and in excellent condition.