1.PM2.5 filtration efficiency is over 97 2.3D split vault skeleton, even breathing even if you exercise 3.Large diameter cold flow breathing valve for smoother air circulation 4.Ultra thin silicone valve, sensitive rebound, high airtightness 5.High efficiency filtration of 5 layer filter material, environmentally friendly polyurethane sponge material, preliminary filtration of large particle impurities such as pollen 6.Double layer melting HEPA, superfine fiber stacking, blocking oily particles and bacteria 7.TPU elastic film composite superfine sponge is more comfortable nbsp