3 Pack Big Blue Water Filter Replacement, 20 Inch (3x5 Micron PP, 3xCarbon Block & 3x1 Micron PP) 9 ItemsReplacement cartridges will fit any 20 inch Big Blue water filter system Stage 1: 3x sediment filter (5 Micron), removes mud, rust, dirt, floating particulates or any other large particles Stage 2: 3x carbon block filter reduces fine sediment, chlorine taste and the concentration of heavy metals such as lead and copper Stage 3: 3x sediment filter (1 Micron), further removes contaminants, oils and up to 60% of bacteria