Our 4.5 x20” Big Blue housings are very versatile as far as the types of cartridge filters that they can accommodate. Depending on how in depth of filtration that you prefer, these systems are available in single housings, duals, and even triples. All Big Blue systems are sent with the mounting brackets/mounting screws, filter housing wrenches, and pressure relief buttons to help ease the filter change. Some people choose three different sediment filters with different micron sizes for effective “step down” filtration. Others choose sediment and carbon cartridges for these. There are many combinations of filter cartridges in regards to this treatment technology.