AA-Racks Model X27 Square 2 Bar Set Rain-Gutter Van Ladder Roof Racks Steel Rack (White) The Three-bolt Lock design makes it compatible to most van rain gutters; while keeping the stability for the loads, it is easy to install & uninstall. The Protective Rubber Covers on both upright clamps prevent metallic friction on the rain gutters, which can also further reduce chance of rusting. The X37-S is built with the thickness of Gauge Grade No. 10 (3.78mm actual steel thickness) for heavy-duty purpose. The X37-S also comes with four Adjustable Ladder Stoppers; (two for each bar), they provide the convenience and security for multiple ladder carrying. The Oval Shape design of the upright clamps is Height-reduced, ( less than 11 while installed ); this design not only prevents water leakage & improves wind noise problems, it also makes your vehicle more accessible to most height restrictions.