The Nap Zapper is a simple device that could just save your life- or help you keep your job! The small, flexible, lightweight device rests comfortably over the top of your ear and will alert you with an audible alarm to wake you if you start to doze and your head nods forward. The Nap Zapper is lightweight and comfortable to wear (approximately the size of an external hearing aid) and is fully adjustable. Perfect for sleepy drivers or someone working the late shift and having trouble staying awake. It works great for security guards, machine operators, and even students struggling to stay awake while studying. The unit uses 3 LR41 batteries that are included. It measures two and three-quarter inches x two inches x one-half inch. Warning: Never drive when you know you are sleepy. Pull over and get proper rest. Do not rely on a drive alert to keep you awake when you are tired.