Pack of 4 - **BRAND NEW** * Mechanical and chemical filter cartridges for Emperor power filters * Traps debris and removes dissolved organic aquarium pollutants * Replace filter cartridge every 2-4 weeks for optimum aquarium water quality Marineland Emperor Rite-Size E Filter Cartridges boast "rinse and drop in" convenience for clean and clear aquarium water. Rite-Size E Cartridges for Emperor 280 and 400 BIO-Wheel Power Filters feature a double-thick polyfiber pad on one side to efficiently trap dirt and debris. The other side features a patented ribbed backing that allows even distribution of aquarium water through the super-effective Black Diamond Carbon that quickly removes discoloration and dissolved organic pollutants. The result is superior mechanical and chemical filtration to maintain superior aquarium water quality. Marineland Emperor Rite-Size E Filter Cartridges measure 9-1/2" x 6". Use one filter cartridge for the Emperor 280 and two pads for the 400. Marineland Emperor Rite-Size E Filter Cartridges Installing your Emperor Rite-Size "E" Filter Cartridge(s) Thoroughly rinse cartridge(s) under cold water to remove any dust. Shake cartridge(s) horizontally (blue side up), to evenly distribute carbon over ribbed back. Slide cartridge(s) into Filter Cartridge Channels (narrow side down, ribbed back facing towards aquarium). Be sure each cartridge is securely seated in bottom channel. NOTE: For optimum power filter performance replace filter cartridge every 2-4 weeks.