Each cartridge acts as a two-stage filter. The dense foam outer layer removes dirt and particulates while inside, the activated carbon removes odor, organics and discoloration. The rigid frame ensures that water passes through the cartridge, and not around it, for optimal water filtration.                                                                                     Aqueon QuietFlow Internal Filter Cartridge. Fits size AT15 and AT20. 

• Aquarium: Filter Cartridges
• Small
• 2 Pk