Gripping Range - 1/8-3/4(1/8,1/4,3/8,1/2,5/8,3/4). High accuracy - Accuracy ground and the accuracy is 0.015mm(0.0006). Material - Made of high grade specially formulated spring steel, first class 1065 carbon steel,durable and sturdy. Clever design - Built in self-Release design and tools will never get stuck in holder. Application - Perfect for CNC milling lathe tool and work-holding engraving machine.