I present my small keychain survival whistle, which emits a clear and sharp signalling note.
This whistle has a screw off back section, which allows the whistle to be used as a storage container, when not in use. Perfect for a keychain, backpacks, or survival kit.
The attachment hole is 4mm wide and 7mm hall, designed to allow two lengths of paracord 550 through.
There are some more photos of this object and other examples of my work, both 3D printed and otherwise, on my 'Tofty' facebook page