The dual HEPA filter, one-size-fits-all, Resp-O-Rator solves the beard problem with a simple "snorkel" design, and a minimum filtering efficiency of 99.97% (down to 0.3 microns). Completely effective in sealing out the lung threatening dust that somehow always manages to seep through other devices.It allows total visibility in all directions. It"s light, comfortable, and won"t conflict with goggles or face shields, hearing protection or hearing aids.Exhausted air is discharged downward to prevent fog-up of glasses. The anti-siphon check valve prevents drawing in unfiltered air. The Resp-O-Rator is best when face shields may be required and for highly strenuous or extremely dusty conditions where higher volumes of air must be filtered.Ideal for shop use and where frequent interruptions for use of the phone, speaking, or drinking are necessary. Made in USA!