This spring collects are made of carbon bearing steel material, heat treated rigidity is HRC48-50, fine durability, can provides long service time. The Specifications are complete, with high accurate processing, high clamping ability, wide clamping ranges. Wide applications, it can be widely used in wire, milling, boring, drilling, tapping, CNC, carving, spindle machine and other processing work. Features: Made of carbon bearing steel material, heat treated rigidity is HRC48-50, fine durability, can provide long service time. All the surface of critical collets are accurate ground for an accurate fit. Alotted alternately from both ends, constructed with high strength, with fine gripping performances. Keep the tools and workpieces firmly to prevents them from wobbling or loosening during machining. They can fit into collet chucks or machine spindles and hold small tool shanks or workpieces. They also center the tools and workpieces to improve cutting accuracy and concentration. Wide applications, it can be widely used in wire, milling, boring, drilling, tapping, CNC, carving, spindle machine and other processing work. Specifications: Type: set A, set B, set C (optional) Material: carbon steel Hardness: HRC=48-50 Specs: Set A (ER11-13PC): 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7 Set B (ER16-10PC): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 Set C (ER20-15PC): 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1/4, 1/8 Package size: 200 * 150 * 100mm / 7.9 * 5.9 * 3.9in Package weight: Set A: 217g / 7.7ounce Set B: 106g / 3.7ounce Set C: 572g / 1.3lb Packing List: 1 * Set of Collets