This alarm is small enough to easily fit in the palm of your hand and can conveniently attach to your key chain so it will be readily available in case of an emergency. The alarm button allows for two levels of protection. Pressing the button slightly will sound a brief alarm blast. Pushing the button down completely will sound the alarm continually until the situation is safe and you deactivate the alarm. The alarm button is recessed to prevent accidental activation. For your added safety, this unit also features a built-in flashlight which emits a bright beam of light when needed. Measures 2.5 inches by 1.25 inches. Requires a Twelve volt battery that is included. The alarm is 120 decibels.