Yakima Fork Tire Wheel Mount
The product itself is great. Far improved over past models with both the stop that keeps the wheel secure and the device which keeps the wheel from spinning.
That said I wish the website would have had dimensions for the mount. With two bike mounts and one kayak mount on top of my Xterra, I had a hard time fitting them (I bought two) on because they were wider than I expected.
Anyway, excellent product. Just make sure you have room on top for the product.