Features: 【Durable Material】Made of high-speed steel material and adopted screw type design, it is durable in use and will not damage bits. 【User-friendly】Meeting professional requirements, the surface of it is smooth and clean. It can be used at will and easily to improve work efficiency. 【Size】8 different sizes Depth Stop Collars Ring Positioners, 3, 4, 5, 6, 8, 10, 12, 16mm Diameter with one hex wrench. 【Function】With the screw set tightly, the collar will remain securely in place which can accurately control the depth of the hole you are drilling. It is for ideal for repeated drilling. 【Use For】Bit limit rings are used as a shaft collar on machinery and can also be used on any type of bit that needs precision drilling, keeping every hole extremely precise. Specifications: Material: High-speed steel Size: 3/4/5/6/8/10/12/16mm 0.12/0.16/0.20/0.24/0.31/0.39/0.47/0.63inches Package Includes: Package includes: 1x 3/4/5/6/8/10/12/16mm Bit Limit Ring note: Please allow 1-2cm errors due to manual measurement. Due to the difference between different monitors, the picture may not reflect the actual color of the item.