Use it to find your car in a crowded parking lot, your campsite, even to rendezvous with your group. It has a weather-resistant and extremely compact design with a fastening ring to stow conveniently in your pocket, pack, or purse. The BackTrack is especially useful at places such as parking lots, malls, stadiums, parks, and festivals. The BackTrack is powered by 2 AAA batteries (sold separately).