Thinner than previous designs, but boasts more surface area to effeciently increase biological activity and trap debris, due to it's unique ripple pattern. Designed specifically for the compact design of the Fluval FX2 Canister Filter. The Fluval FX2 Bio-Foam maintains even flow, enhances the biological filtration process and has ideal pore size for most effient water flow and a longer lifespan of filter media.