SAFETY WORKS Toxic Dust Replacement Cartridge, Filter Rating: P100, Suitable for: SWX Series Full Face pieces or Half-Mask Face pieces RespiratorToxic Dust Respirator long-life cartridges are approved to the NIOSH (National Institute for Occupational Safety and Health) 42 CFR 84 respirator certification regulations, under the P100 Class, so they are at least 99.97% efficient against oil- and non-oil based contaminants, and are oil-proof so they have no time use limitationThese P100 cartridges feature rear-entry air flow that helps keep debris out of filter and makes respirator fit checking easierThese cartridges are low-profile for improved field of visionThese cartridges are only compatible with SWX series Full Facepieces or Half-Mask Facepieces