A. Multipure uses coconut shell to make their solid activated carbon block filters because coconut shell produces the smallest pore size and are the purest form of carbon known in the world. Almost 85-90% surface area of coconut shell activated carbon exists as micro-pores. These small pore sizes match the size of contaminant molecules in drinking water and therefore are very effective in trapping them. Multipure solid activated carbon block pore size of 0.5 micron (micrometer) made from coconut shells exceed industry standards and is equivalent to one thousandth of a millimeter or one millionth of a meter or one 50th of a thousandth of an inch, establishing standards and quality on which you can depend.