H6 Advanced Breathing SystemThe larger air intake tube can provide users with fresh air more efficiently, and the three exhaust ports can more easily exhaust all the exhaust gas. The exhalation and inhalation systems are separated, so that fresh air and exhaust gas will not be mixed in the mask and cause dizziness. Compared with ordinary diving masks, this latest system allows users to experience snorkeling for a longer time, provides users with a safer and smoother breathing experience. Double Floating Balls DesignThere are two floating balls on the top of the air intake tube. When the trachea is submerged in water, two floating balls will float up and block the air inlet tightly, preventing the user from choking water due to water entering the breathing system. The double floating balls design makes the Anti-Leak function of this snorkel mask more reliable. Dual Anti-Fog 180 Clear ViewThis snorkel mask is equipped with transparent flat lenses to eliminate all dizziness caused by distortion of the field of view. The "mirror optical polishing" process greatly improves the clarity of the mirror, allowing users to appreciate the 180 underwater world more clearly. The snorkel mask has a physical anti-fog system, and we also added an anti-fog coating on the lens, double anti-fog make users to experience fog-free snorkeling. Ergonomic DesignThe wearing part of this product is made of food-grade silicone and high-quality elastic band, which is non-toxic and environmentally friendly. The ergonomic design allows users of various face shape to wear it comfortably. If the distance from your chin to bridge of nose are more than 4.7 inch(12cm), we sugggest that you choose L/XL, if between 4.7 inch and 4 inch, we sugggest that you choose S/M.