SPECIFICATION --- Wide range of collet sizes from 2 to 13 mm/0.04 to 0.51 inch, suitable for many types of drills. Diameter: 43 mm; Length: 71 mm; Connection size: 1/2-20UNF; STRONG CLAMPING FORCE --- The unique design can easily convert the torque exerted by the handle into greater clamping force and hold the drill firmly and securely, which is not easy to loosen. EXCELLENT PERFORMANCE --- The keyless and self-tightening design is more in line with human engineering. Thanks to heat treatment, the product has good toughness and superior structural strength. EASY TO USE --- Durable and long-lasting, suitable for long-term work. Easy to install and disassemble, more convenient and economical. Have good metal structure and nice coating surface.