This inexpensive, imported strobe is waterproof to 40 meters. The xenon gas light runs up to 28 hours on a single, alkaline C cell. The SOS Light comes with a hook and loop strap for attachment to your arm, leg, pack or PFD. Small size and light weight make it easy to pack, carry, or wear. Meets USCG and SOLAS requirements when used with lithium battery. Lithium battery has a 5 year shelf life and a running time of 24 hours. Battery not included.