This replacement filter cartridge replaces Unicel # C-4340, Pleatco # PMT40 and Filbur # FC-3081 and meets OEM # 1561-03 specifications. This 11 5/8 inch long and 4 15/16 inch wide filter cartridge is capable of handling the top load of 40 square foot and the most suitable for Dimension One Spas. It has 2 1/8 inch open holes both at the top as well as bottom. By installing it you get complete protection from germs and sand in your pools and spas. Very easy to install this filter cartridge is made of high quality of materials.