A weatherproof lightweight mini speaker system that attaches to any backpack straps - brilliant! The Music Strap offers high quality sound safely with no ear buds. A great addition to hikes, campsites, bike trips, and playrooms - for adults too! The 1.0 watt speakers are compatible with MP3 players and iPods offering clear sound. The speakers have a 20 inch audio cable, 27.5 inch speaker cable, 2 Mode LED red lights (solid & flashing), cable ties secure speaker cable to pack, and the speakers are contoured to fit all backpack shoulder straps. Listen to music still maintain some awareness of your surroundings. Requires 2 AAA batteries (not included). Fits any size backpack with shoulder straps - for kids & adults too!