The 3 in 1 emergency whistle is an ideal piece of survival equipment that is essential for a hiking or walking trip. The 3 in 1 whistle has a small compass on one side & a thermometer on the other. A nylon neck lanyard means you can wear the emergency whistle around your neck or attach it to the outside of your backpack. The whistle is great for camping, hiking & walking. The 3 in 1 whistle is light weight measuring 3.2cm by 6cm.