N99 NASK Smart Mask. 99% plus filtration. 50 pcs per box. Bacterial Filtration Efficiency (BFE) up to 99%, Particle Filtration Efficiency (PFE) up to 99%, Viral Filtration Efficiency (VFE) up to 99%, Blood Splatter within ASTM F1862 , Ultralight and breathable, Conforms with NIOSH criteria.