Waterway Plastics 502-9910 Cartridge Filter, Waterway Top Load, 100 sqft, 2"sWaterway Plastics filter model 502-9910 is a 2"s top load filter. For use on portable spas, it is designed to mount in a niche so that the main body is under the shell of the spa, while the top is accessed from above the spa. This complete filter includes a niche lock ring (secures the body to the niche), lid lock ring (secures the lid), 100 sq. ft. cartridge, and lid w/o bromine feeder tube.