This is a great light for both safety and fun. The four super-bright LEDs can be seen from one mile away! The reflector background means the light will draw attention even if the LEDs are off. A strong magnetic back allows you to attach this easily to your car, bike, etc. and it even comes with an adhesive metal strip, so you can stick the strip to a backpack, tent, or wherever and attach the blinker light to it. Also great to just carry in your hands as a neat multi-color LED club toy. The blinker is about 3" long x 1.25" wide. Uses 4 replaceable AG13 batteries (included).