2pcs of Block Activated Carbon filters – 20" Big Blue Block Activated Carbon filters are similar in their performance to that of GAC filters, being made of fine coconut shell carbon they also do remove odors and tastes of many organic compounds, chlorine especially. Though, because this filters are made of a packed carbon (forming a cylinder block), they offer a much finer filtration of suspended particles and dirt. 2 pcs of Melt-blown Polypropylene Sediment filters – 20" Big Blue Sediment filter is often the first filter installed in the Whole House Water Filter. Sediment filters are made of fine melted polypropylene, which is then blown and spun in a cylinder-like form. The main function of a sediment filter is to remove large and fine particles from a drinking water, such as sand, dirt, silt, and rust particles. Removal of such particles allows for a better performance of all the following filters, such as Carbon Block or GAC filters.