This is a great whistle very similar to many whistles available from places like REI or Eastern Mountain Sports. Its is compact, since rather than using a cork ball, it simply uses air. It is cheap and only requires a bic pen. It also makes a great addition to survival kits, such as the Altoid Survival Kits found on Instructables. (See link.) This is my first instructable, so I decided to start with something simple. Please drop me a comment.