This NU Aqua Granular Activated Carbon Filter or GAC filter is a direct replacement for the NU Aqua Whole House Water Filtration System. This filter is 4.5” x 20” and will directly work with most standard whole home systems. Manufactured using HydraCoil technology these filters provide a higher absorption rate due to the molecular structure of the pores becoming more permeable which allows even the smallest of particles to be efficiently removed from your water. With a ten times chlorine absorption capacity these filters are the premier carbon block filter on the market.