This spring collects are made of carbon bearing steel material, heat treated rigidity is HRC48-50, fine durability, can provide long service time. 18PCS in a set, the specifications are complete, with high precise processing, high clamping force, 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 precise ground for an accurate fit. ER collets are slotted alternately from both ends, constructed with high strength, with better gripping performance. 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. 18PCS in a set, the specifications are complete, with high precise processing, high clamping force, wide clamping ranges. Wide applications, it can be widely used in wire, milling, boring, drilling, tapping, CNC, carving, spindle machine and other processing work. Specifications: Name: Spring Collets Set Material: carbon steel Hardness: HRC=48-50 Type: 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 Package size: 220 * 80 * 40mm / 8.66 * 3.15 * 1.57in Package weight: 2500g / 5.51lb Packing List: 1 * Spring Collets Set