Made in USA by Dubuque Clamp Works, these aluminum bar clamps are lightweight, extremely rigid, and easy to adjust. The heat-treated, extruded aluminum bars measure 1-3/8 x 7/8 in. and have side walls nearly 1/8 in. thick for excellent resistance to bowing and twisting. The adjustable head has a spring clutch for easy adjustment along the notched bar, and the fixed head has a 1/2-in. diameter Acme-threaded screw and wing knob for final tightening. Because these clamps remain reliably straight under clamping force, you can clamp your workpiece against them to prevent misalignment. 1000 lb. load rating. 36" clamp capacity.