It's a yo-yo! It's a keychain! And yes it works!
At 1-1/2 inches in diameter (3.81 cm) it's small enough to fit in your pocket, and at 35 grams it is heavy enough to use. When we first picked this up, we were shocked to be able to do a brain twister with this on the first try. It sleeps as well as (or perhaps a little better than) a regular Duncan Imperial. It is a poor looper, but it is a must-have for your pocket. Just pop off the rubber ring that holds the yo-yo to the keychain ring, and yo! Pop it back with your keys when you are done. It comes on a blister card showing the Duncan yo-yo man.