The Adventure Lights Dual Function Guardian Dog Light is the toughest light of it’s kind. Waterproof to 300 feet(100m), impact resistant, and able to withstand extreme temperatures. Each light comes with a battery pack(2 x 2032 lithium), locking belt clip and velcro collar attachment. Change functions from steady-on to strobing by simply flipping over the battery. When being seen is a priority, this light will strobe for up to 240 hours or 100 hours of steady-on. Weighing less than an ounce(0.8) this product was designed for and still in use by the Military.