They're invading. Seriously. I sold like five of them in less than six hours. Accounted for maybe a fifth of my revenue that day. There can be only one response: MORE KEYCHAINS.
I might consider making a how-to on them, honestly. They're not that hard. The hardest part is when the rings are just a wee bit too small and you really have to force the dratted last few links together to make it solid.