This 75 sq. ft., 9" OD Pool or Spa Filter has a 4" Open Hole Top, a 4" Open Hole Bottom, and is 11 7/16" long. It is crafted of the highest quality materials; and engineered to be superior. With USA MADE REEMAY, the highest quality fabric that removes unwanted bacteria and contaminants, keeping your water crystal clean.Our Pool and Spa Replacement Filter Cartridges meet or exceed OEM specifications. They install easily, and begin working to clean water immediately. Once you have tried our filters, you will see how they filter out more debris than the other brands, and out last other brands.Guaranteed Perfect FitFilters Bacteria & ContaminantsEco Friendly Filter CartridgeExtremely Durable - Wash & ReuseWithstands High Pressures & TemperaturesEnergy EfficientEasy InstallationHint: keep an extra filter on hand so that when its time to clean your filter, you will be able to replace it immediately with the back-up.This will allow you the time to leisurely deep clean your dirty filter and allow it to dry completely before replacing it; and without any down time on your pool or spa system.