We bought these for cross country skiing just in case we got separated. Never had to use them. The whistles are two different colors so you can see which is yours at a glance. The Classic Fox 40 Safety Whistle is the original and still the standard choice for rescue professionals. Sometimes you have to be heard to be rescued.The 3-chamber pea less design has no moving parts to freeze, jam or deteriorate.Easy to blow and cannot be overblown. The harder you blow, the louder the sound.Chambers are designed to self-clear when submerged in water.Sound will be heard up to a mile away.A whistle is vital for signaling above the sound of surf and whitewater.Remember, in most on-the-water situations a sounding device like a whistle is required by the Coast Guard.Two whistles, one White and one Teal Green.Each whistle comes with a standard black lanyard.