2 pack, toxic dust respirator replacement cartridges p100, compatible with toxic dust respirator, heap level filtrations, high efficiency particulate air heap filters are 99.97% efficient against particles which are at 0.3 microns or larger, designed with pleats, these patented cartridges feature a large surface area in a very small diameter, low profile, respirator is approved by niosh under the niosh 42 cfr 84 respirator certification regulations & approved for the p100 filter classification, use with swx00319 toxic dust respirator.