How to choose the size? Firstly, Measure the distance between the sides of your cheeks . If the length is 12.5cm(4.9 inches) , it's suitable for size S/M. If the length is12.5cm(4.9 inches),it's suitable for size L/XL. Description: 1.Safety Airflow System: The upgraded snorkeling mask features a fully dry snorkeling system, which reduces the length of the snorkeling tube and increases the diameter to allow faster exhaust and better breathing. With the movable float ball design, it can effectively prevent water from flowing into the top, which eliminates the possibility of water entering the breathing tube to prevent choking, it allows you to enjoy snorkeling, free diving or swimming. 2.Professional Anti-leak Design: Snorkel mask follows the design of human face engineering. Compared with the traditional solid silicone skirt, our soft liquid silicone skirt is formed in one body, which can perfectly adhere to different face shapes and maintain a high standard of leakproofness and comfort. The drying system is built-in silicone seal in breathing tube, which can effectively prevents water from entering the mask and allow you to enjoy the underwater world safely. 3.Ultra-clear Anti-fog Design: Snorkel set is made of professional high-definition anti-fog flat lens, with wide field of vision, high transmittance and no dizziness. The nose cover is made of liquid silica gel, which fits perfectly with the nose and the breathing passage is completely isolated from the lens, prevents fogging. Our snorkel mask can also be used as swimming goggles, diving goggles. Complimentary camera stand allows you to record every beautiful moment underwater. 4.Comfortable and Lightweight: Compared with the full face type, the snorkel gear won't make you feel stuffy in summer, and the weight is only a quarter of the old full face snorkel mask. The snorkel set comes with adjustable straps that allow you to adjust to the most comfortable fit.Breather tube is detachable and foldable. which is light and small, easy to store and carry. 5.High Quality Material : snorkel gear is made of high-quality PC and food-grade liquid silicone, safe and environmentally friendly, non-toxic, non-odor, non-allergic, easy to clean, and especially suitable for long-term use. Specifications: Material:liquid silicone Universal size:Fit For Kids Adults(suitable for over 4 years old) Size S/M is 12.5x11 cm(4.9x4.3 inch) Size L/XL is 13.5x12 cm(5.3x4.7 inch) the net weight is 368g (0.8 lbs) colour:Blue / Green / Black/ Red/Transparent 180 degree panorama Package Contents: 1 * Snorkel Mask Notices: 1) There could be some slight differences in the color tone of the pictures and the actual item. 2) Please allow 1-2mm differs due to manual measurement, thanks. 3) If there is any problem with the product, please contact me before you leave a comment, I will do my best to solve the problem for you.Thank you for your understanding.