Frodo, that's not a stupid question. For reassurance, go check some of the questions I've posted.
The flat gel pad is about the size of my hand, but only about 1/8" thick. It's not a mouse pad. I think they're mostly used to keep things from sliding around, and they do a good job of that. The Officemax I got mine from had them up by the checkout counters, and I got a nice black one that blends in very well with my dash.
Kavlono, before you give up on the GPS, bmussatti has posted good advice. I was actually a little skeptical that the air vent mount would work very well - especially at the price. But it's been great.