500/case (10 boxes of 50), 99.3% Filtration Efficiency @.1 Micron per ASTM F2299. - If you have skin sensitivity, choose the CoolOne Sensitive Skin Mask. These masks are hypoallergenic and free of pigments, dyes and latex. The patented Magic Arch support strip holds the mask away from the nose and mouth to create a larger breathing chamber without limiting downward vision. This results in cooler, more comfortable performance. For a secure, comfortable fit, soft knit ear loops are ultrasonically welded to the mask. Anti-fog style prevents protective eyewear from fogging.