Proburger Clamp - Swivel with roll pin for fixed option. Couplers are constructed from a certified high tensile-strength 6061 T6 aluminum extrusion. They attach securely to tubes and combine strength and durability with a high degree of safety. Proburger clamps are rated clamps that work on 1-1/4", 1-1/2", and true 2" pipe (truss/camera car). These clamps are rated at 1100 lbs (500 kg) load capacity.