https://www.printables.com/model/495173-flat-pocket-whistle
With a thickness of only 3 mm, the flat whistle fits in any wallet. Despite its flat design, it’s really loud. It is also possible to wear the whistle as a chain or attach it to a keychain. It has a clear double tone. Due to the size, the sound is quite high. But it is enough to get attention.
hamza –
super loud, easy to carry, sleek and smart. What more could you want from a whistle?
Syed Ayyan –
What hamza said
Mohammed Safwan Khan –
One of the best whistles you can find online. Very cheap, portable and small. Keep up with your work