Why transparent? So you can see what your cartridge has caught. Rated to 5 microns, it traps sediment and particles at that size and larger, and the pleats change from white to amber, brown or grey. Understand the water in your home.

After the 5 micron stage, water passes through three more layers: KDF-55 removes metals, calcium sulfite blocks chlorine, and activated carbon filters the water.

Every home's water is different, city or well. Replace based on what you see, not an industry schedule, up to the cartridge's maximum service life, so you don't replace too early or too late.