These NEW steel stops attach to your Thule AeroBlade or AeroBlade Edge bars to keep your gear in place. These Aero load stops make Thule the best choice when you want a rack system to carry lumber or other items that need to be tied down. These allow you to pass a 523 Load Strap or any other strap through the Aero Load Stop, and around the load. These make for a rock-solid carrying base. Perfect for lumber, ladders, and siding.