Material: Drill stop collar made of high quality carbon steel, durable and reusable, will be firmly fixed at the place of placement, and not easy to slip, damage the drill.Assorted sizes: 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm. Comes with 1 set of drill limit rings (8 pieces in total) with 1 Allen key. [Easy to use] Just select the appropriate depth, slide the stopper on the drill, adjust the required depth with a ruler, and then tighten it. Do not run the drill at high speed - it is out of balance. DRILLING DEPTH CONTROL: Use the 8-piece DCT Adjustable Screw Lock Collar to precisely control the depth of a hole you are drilling; great for drilling depth when precise measurement is needed for hole depth; designed to hold your bit securely in place and grip the full diameter of your bit without the screw ever touching the shank. Widely Uses: The drilling depth stop set is used as a mechanical collar, perfect for precise drilling, which is suitable for production and repeat drilling work, suitable for wood or wall drilling.