1、Emergency Whistles: When diving in distress, trapped, emergency call for help, send out high voice frequency distress signal. International SOS whistle: three short, three long, three short.2、Premium Material: The emergency whistle is made of pp material refined, lightweight and portable, wear resistant and durable, integrated design, strong and reliable.3、High Decibel Sound: The left and right sides simultaneously produce high and low audio, and the sound is loud and bright, with strong penetration under different environmental conditions.4、Special Design: With back clip and plastic quick shackle, can be hung on the belt, D ring, also can be clipped on the clothing backpack, easy to carry.5、Good Performance: The survival whistle is one piece design, there is nothing to obstruct sound and nothing to jam, break or freeze for good working performance.