The Thule 523 - Load Straps are heavy-duty multi-purpose straps with cam buckles. These Thule straps are designed for easy of use, strength and to be gentle around a vehicle. The straps use rugged, chromated steel cam-action buckles that do not require any knot tieing. Simply run the end of the strap through the buckle and pull out the slack. The cam-action will no let out slack until the release button is pressed. The 15 foot straps are made of strong polypropylene nylon that will not stretch and will not weaken after prolonged exposure to moisture and sun light. Unlike big, complicated ratcheting type buckles that can easily swing out of control and ding or scratch a vehicle, the rubber bumpers that cover the Thule cam buckle protect the vehicle from its metal buckle.