3M 2091 Particulate P100 filters attach directly to 3M Half-Face and 3M Full-Face reusable respirators. If using in conjunction with a cartridge, a Filter Adapter is required. These filters offer superior protection to N95 masks when used appropriately with approved respirators. "P"= Oil proof, resists oil for up to 40 hours. 100 = 99.97% of particles filtered.