IRWIN RECORD 121 Series G-Clamps
121 Series: These are the strongest G-Cramps you can buy with the Drop Forged Steel Frame giving a proof load of up to 15000lbs (6,800kg) on the largest size. The steel mainscrew has a large swivel shoe to cater for uneven surfaces and a fast acting thread that is rolled into the steel for strength and resilience. They are recommended particularly for metalworking and fabrication work where very high clamping pressures are demanded.