How to choose the size? Firstly, Measure the length from the Eye to Chin. If the length is 8.5-10 cm (3.35-3.94inch or less) , it's suitable for children . If the length is 10-12 cm (3.94-4.72inch) ,it's suitable for Teenager . If the length equal with or over 12 cm,it's suitable for Adult . Description: 1. 180 Full Face Design: Different from other traditional snorkeling goggles, our face protector can provide you with wider vision, thus opening up a whole new world of underwater adventure. 2. Breathe freely and safely: Its full face design allows you to breathe comfortably through your nose and mouth while diving. Using advanced leak-proof technology, this can maximize safety and ensure that you inhale fresh air every time you breathe. 3. Anti-fog and anti-leakage: Independent inhalation and exhalation channels can prevent the mask from fogging. In addition, it has anti-fog coating on the lens and anti-fog insert; in addition, its advanced leak-proof silicone sealing technology (With float) can prevent water from entering the mask. 4. Comfortable to Wear: This adult diving face protector is made of hard polycarbonate, non-toxic and odorless; it is wrapped with soft and thick imported medical liquid silicone + elastic elastic band, which can ensure your safety and will not hurt your head for a long time; Breathe freely, no need to grasp the breathing tube with your mouth and chin. 5. Beginner-friendly gifts: Our masks are easier to use than traditional diving masks, and are more friendly to beginners and young people, making them perfect gifts for friends and family. Enjoy an unforgettable vacation with this sports snorkeling mask. Specification: Shell material: polycarbonate (PC) Inner shell material: imported medical liquid silicone + elastic elastic band Color: blue, black, green, pink Size(approx.): children smaller size(XS Size): inner diameter 11*12CM ,outer diameter 14.5*17CM adult small size (S/M Size): inner diameter 17*13CM, outer diameter 23*19CM adult large size (L/XL Size): inner diameter 19*13CM, outer diameter 23*19CM Packing Contents: 1 Pc x Diving mask