ZJchao ER20 Precision SPRING COLLET set 13 pcs (1mm-13mm) CNC MILLING LATHE CHUCK TOOL Made of high grade specially formulated spring steel Hardened and precision ground Built in self-release design and tools will never get stuck in holder Big clampingforce andwide clamping range, widely used in machining centers,general milling machines, CNC milling machine, engraving machine, high-speed machines, and other processing