The Rescue Howler Whistle emits a piercing dual-frequency 110dB signal thanks to a dual-chamber, fail-safe, pea-less design. Made from unbreakable ABS plastic for a lifetime of trouble-free use. Be heard, 110dB signal is audible over 1 mile (1.6 km). Fail-safe, pea-less design works in all conditions - won't freeze or stick to lips when cold. Intense sound whistle has a triple-frequency sound cuts through surrounding noise for long range signaling. Each whistle comes with a split key ring for attachment to gear or a Personal Floatation Device (PFD). Whistles are ideal for Ideal for skiing, snowboarding, hiking, backpacking, alpine, rock climbing, mountain and road biking, off road activities, paddle sports, marine and emergency prep. Each whistle measures 2.125" x 0.25" (5.4 x 0.64 cm), weighs 0.2 oz. (5.67 g) and is designed for 2 persons for a multiple days.