Ultimate Hummers Magazine

[Adam in CO]

No, it's a sealed metal ring that has synthetic fluid and bb's in it. You mount the ring behind the tire.

http://mrtruck.net/h1centra.htm

When you accelerate from a stop, the bb's find the unbalanced spots, and re-balance the tire every time you hit the gas. It's a very cool idea, but they have not mastered a way to make them properly for the front tires on an H2, because the calipers are too big.