Irwin record heavy duty 120 series g clamps are the strongest record clamps recommended particularly for metal working and fabrication work where a very high clamping force is demanded they have a drop forged steel frame for strength and durability with a swivel shoe which helps clamping on uneven surfaces the twin start acme cold rolled thread for faster operation and the fused steel handle will bend before the clamp can be overstressed a popular general purpose clamp for heavy duty application