I really, really, really, love these little guys. I use them as covert shoelace keys. With a little heat shrink tubing you can turn the tip of your shoelace into a covert key. It makes for successful escape and evasion.
As an emergency back up, single use concealable key, its a reliable choice. A stiffer material (resin?) and, perhaps, more ergonomic grip would make it a 5. Pair this in a shoe or belt (or? EDC) with half a small, ceramic blade and you have a decent and tiny escape kit.