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.