The Adventure Lights Guardian TAG-IT is the toughest light of its kind. Waterproof to 300 feet (100m), impact-resistant and able to withstand extreme temperatures. When being seen is a priority, this light will flash for up to 240 hours or stay steadily illuminated for 100 hours. Each light comes with a battery pack (2 x 2032 lithium). Function is changed from steady-on to flashing by simply flipping over the battery. Equipped with a clip base, these lights can be fastened to the loop of your dog's collar, as well as backpacks, water bottles or apparel of your own.