Everpure EV927075 H-300+HSD Water Filter Cartridge Reduces lead to below the Federal Action Level of 15 ppb Reduces cysts such as Giardia lamblia, Entamoeba histolytica and Cryptosporidium parvum Reduces lime scale build-up in appliances that use water HSD stands for high silt density. This cartridge is made for use where the water contains particulates.