This Replacement filter cartridge had the technical specifications as Unicel # T-380R and Filbur # FC-3061 and it complies with the OEM # T380R specification. This 9 ¾ inch long and 2 ¾ inch wide filter cartridge has open holes of 1 1/16 inch both at the top as well as bottom. It is capable of handling the top load of 6 sq. ft. and best fit for Harmsco ST/6, American, Pac-Fab, Premier, Rainbow, Swimquip, SwimRite. By installing this you get clean and clear water free from dust, sand and worms. Very easy to install this filter cartridge is made of high quality materials.