size: XS is for children S/M size: inner diameter 17*13CM, outer diameter 23*19CM L/XL size: inner diameter 19*13CM, outer diameter 23*19CM Features: 1. The mask is not suitable for scuba diving, only suitable for snorkeling and swimming training; 2. Do not press the facial silicone on the hair and beard when wearing it. It is recommended to use it after shaving; 3. This product is only for snorkeling and swimming assistance, not for life-saving purposes; 4. Children need to be accompanied by adults for better effect; 5. The best use effect is in the temperature environment of 18-45 degrees; 6. Do not expose to the sun; 7. After using in seawater, it is recommended to soak the powder in warm water for a few minutes before cleaning, which can prevent salt scale; 8. This product is recommended to be wiped with a glasses cloth or a dust-free cloth, or directly rinsed and then air-dried. Do not wipe the mirror surface directly with your hands or with an ordinary cloth to prevent random flowers; 9. Do not soak with laundry detergent or detergent products. 10. Exhaust fan principle design, effective anti-fog, no need for breathing tube, DRY DOP system, the top valve automatically closes after entering the water to prevent water from flowing in, elastic headband, easy to wear without hanging hair, ultra- wide shatter-resistant mask