I got this Hummer H2 with Mattracks on sale after Christmas. It was only $60. I wanted the Mattracks, which I have now found out that I can order by themselves from Radio Shack (two sets are about $60). I now have three pair.
Lots of folks are using these for
tracks on their robots and they are what my friend StampNut2 is using on his WALL-E robot which you can read about here. It takes a little work to hack them to fit, but they work really well once you do. You can see good picture of them mounted on a BOE-Bot here.
Here is a litte video too that shows the Mattracks in action. This was made by another person who attached them to their BOE-Bot.