Solar Light Whistle Set of 3 No batteries required. The light turns on with solar charging, and the whistle can be blown. It can be used as a keychain and is convenient to carry. How about for nighttime roads, dark places, or during disasters? I use one myself. The brightness is so-so, but I use it when opening the lock when returning home, and it's useful in places without streetlights. It's small and light, so I carry it in my pocket. Brand new, unused.