I purchased these whistles for a large youth group about 3 years ago. Best purchase ever! We wanted to have all the same whistle so that we could identify the sound as one of our group. We thought that was important. We use the whistles for all our events as emergency whistles only. We have used them for hiking, boating and climbing. We issue one to each new member and so far, knock on wood, we havent had to use them! The only thing I would do to improve them is to make them glow in the dark!