The Sherpa Roof Bag gives you additional cargo carrying capacity at a great value. It mounts quickly and conveniently on the roof, even if you only have side rails, and collapses and compacts for easy storage. The Sherpa can carry up to 13 cu. ft. of cargo, protected by its durable, weather resistant construction. The Sherpa mounts directly to most original equipment and aftermarket crossbars with the included straps.