Medtex M4U Fabric MaskSize: Same as a standard disposable surgical mask. Has been tested and shown to filter 95% of 5 micron particles, even without a filter. Easy to breathe with its unique Medtex 3 layer muslin fabric structure. Reduces the buildup of dirt with a 3 pleat downward shape. The outer layer is made from high quality COTTON USA fiber with water repellent properties, preventing droplets from entering the nose and mouth. The water repellent agent is PFC free,