The Fox 40 line of whistles are the loudest available. These are the same whistles used in sporting events to be heard over the noise of the crowds and even water polo where players wear protective ear pieces and may be under water. There"s no movable ball inside that can get stuck, it"s just one solid piece of plastic so there"s no fear the whistle won"t work because it"s frozen shut. Every survival kit and outdoor pack should have one with their camping equipment. Whistles are also better than shouting for help if you find yourself walking in places that could be considered dangerous. The Mini is just slightly smaller than the Classic and slightly lower pitched.