Features: 1. Has the function of fixed on the bit, limit the depth of the drill holes, bring more convenience to your work. 2. Made of high quality carbon steel, is sturdy, durable, corrosion resistant, and has long service life. 3. The diameter of the positioner are different in 3,4,5,6,8,10,12mm, the various specification can better mee your needs 4. Small size, light in weight, is easy and convenient for you to operate and install it, no other complicated steps are required. 5. Comes with a hex wrench, to better meet your needs, provide more convenience for operation, saving your cost and moeny. Specifications: Material: Carbon Steel Diameter: 3,4,5,6,8,10,12mm Package Included: 7pcs drill bit stop collar set + Wrench .