Fluval Foam Pads are specially designed for Fluval FX5 and FX6 High-Performance Canister Filters. The pads capture large particles and debris for effective mechanical filtration, the crucial first stage in the filtration process. Custom-fit to prevent bypass, they have a pore size that allows efficient water flow with less clogging for long-lasting filtration. Captures Large Particles and Debris for Effective Mechanical Filtration Provides Crucial First Stage in the Filtration Process Pore Size Allows Efficient Water Flow With Less Clogging for Long-Lasting Filtration For Freshwater and Marine Aquariums For Fluval FX5 and FX6 High Performance Canister Filters