A 5.0 micron coconut shell solid carbon block cartridge is utilized as the Stage-1 Filter in our Twin Ultimate Water Filters. Combining the highly absorptive efficiency of a Solid Carbon block with several layers of sediment prefiltration (5 microns) to effectively reduce chlorine tastes, sediment, particulate matter and odors. It also increases the overall life and effectiveness of the Stage 2 - 0.5 micron Ceramic/Activated Carbon water filter (included). The WR002 water filtration set typically lasts for 600 gallons. Ships FREE in continental US. Retail Price: $110.00. The WR002 water filter set includes both cartridges for our WU004 Twin Ultimate Water Filtration Systems.