Spikes-Spider Apline traction device is excellent for use on ice and snow depth 6" and more. Alpine provides the most agressive traction available on deeper snow and steeper grades and slopes. Composed of a steel traction trac, combined with sharpened steel cross members, make for the most agressive traction available. The four arms are strong, composite metal. Four support arms connect to the trac between the arms, so the tires are encircled on the outside portion. The traction ovals are just as easy to put on as the Quick, Sport and Compact style. You just lay the trac on the top of the tire, center the traction oval on the previously installed steel hubs, lock on the holding ring, with a "click". Repeat on the other drive wheel. Drive a few revolutions and the traction ovals are forced by the four arms to self-mount on each tire tread. As with all Spikes-Spiders, the Alpine Pro cannot damage alloy wheels or interfere with vehicle braking, ABS, steering or suspension systems. The Spikes-Spider systems are especially designed to give safety in bad conditions, with the advantage that anyone can fit on the vehicle in only one-half minute for each side and can be removed just as fast. The Alpine Pro stores reasonably flat in the carrying case, so they take up a little less room than the Quick, but about the same as the Compact and Sport styles. Alpine Pro provides the most aggressive traction available on ice, snow, mud and wet grass for vans, pickups, 4x4s, SUVs and emergency service vehicles with large tires.