KX Matrikx ® PB1-20-Green # 06-250-20-Green 0.5 Micron 20' Extruded Carbon Block Water Filter. Lead, Cyst, Giardia and Crytosporidim Reduction. 20" long X 2 1/2" diameter OD X 1 1/4" diameter ID. 20 per case, sold individually. Order a case and save even more.MATRIKX® Pb1® filters, powered by GREENBLOCK®, are made from 100% coconut shell carbon, a renewable, and ecologically sustainable material. The carbon is processed into blocks using a unique binder system and proprietary manufacturing techniques to produce filters with a greater number of micro-pores and available carbon surface area, which display superior adsorption capacity and kinetic dynamics.