... shape, and use the opposite direction fold style,easy airtight. It is wearing comfortable, and applicable to more than 95% of adult ... citizens to wear. The full-eyepiece lens is made from polycarbonate, and it has an open filed of vision,excellent property of optics ... the different kind of toxic. Its life time is long, resistance is small, and it is also light and changed easily. 3. Technical Standards3 ...