Designed to protect athletes exercising outdoors, the Runner Personal Alarm features a piercing, 130dB alarm to call for attention up to 1,000 feet (300 m) away, help scare off attackers, and is fully reusable. Length ranges from 5.5" to 8" , one size fits all. This sweat- and weather-resistant alarm is comfortable and includes an easy-to-use Velcro closure. Reflective material helps cars and witnesses locate you in the dark. Replaceable 4xLR44 batteries with low battery test button included to ensure your device is working when you need it most. Simply pull the metal ring to operate (easy to operate under stress); a self-defense option for any age.