I'm assuming some on this thread have never locked up, or down, in some of the LARGE concrete walled locks on the TN River or Tenn-Tom Waterway, or other river systems - large ie 70-95' tall. As you are going up and the swirling water pushes your boat against the grimy concrete walls - the fenders are crushed (ours are 12" dia. Taylors), and they take a real beating. It takes four of these fenders (on one side) in these locks to keep the boat off the walls. Any covers would be shredded in short order, and any white fenders will be dark soon.