When I was checking them out they looked to be a little smaller then a deck of cards. I didn't like how small they were because I have a bad habit of losing things and thought that I would rather not take the chance, so I purchased the regular sized one.
They are about 4in by 4in at least that is my best guess without actually measuring the thing. They are great for those that just want to listen to music and carry them in your pocket. I actually had one and sold it because it was too small for me.