Made of high grade specially formulated spring steel,powerful clamping ability, and is durable. Hardened and precision ground,built in self-Release design and tools will never get stuck in holder. Premium grade special alloy steel with a high modulus of elasticity ER Collet features full length slits, enabling the collet to collapse uniformly to provide a concentric and full 360 degree gripping surface. Widely used in machining centers,general milling machines, CNC milling machine, engraving machine, high-speed machines, and other processing, Weight: 0.05070632026 Pounds, Manufacturer: Guangzhoujiajimaoyiyouxiangongsi