Product details:

UC-900-48 inch Alum Bar Clamp. Made in USA by the Dubuque Clamp Company, these aluminum bar clamps are lightweight, extremely rigid, and easy to adjust. The strong extruded bars measure 1-3/8 inch x 7/8 inch and have side walls nearly 1/8 inch thick for excellent resistance to bowing and twisting. The bar remains reliably straight under clamping force, so you can clamp work against it to prevent misalignment.The movable head has a spring clutch for fast adjustment on the notched bar, and the fixed head has a 1/2 inch diameter Acme-threaded screw for final tightening, with a large, easy-to-turn wing knob. 1000 lb load rating. Maximum opening capacity listed. This set comes in a pack of 10x clamps.