Description Material: Drill stop collar made of high quality carbon steel, durable and reusable, will be firmly attached to where you put it, and not easy to slip or damage the drill . Assorted sizes: 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm. Comes with 1 set of drill limiting rings (8 pieces in total) with 1 Allen key. Easy to Use: Just select the appropriate depth stop bit, slide the stopper on the drill, set the required depth with a ruler and then tighten. Do not spin the drill at high speed, it is out of balance. Drilling Depth Control: Use the DCT Adjustable Screw Lock Collar with 8-Piece Drilling Split Ring to precisely control the depth of a hole you are drilling; great for depth drilling when precise measurement is needed for hole depth; designed to hold your drill bit in place and grip the entire diameter of your drill bit without the screw ever touching the shank. Wide Applications: The drilling depth stop set is used as a mechanical collar, perfect for precise drilling, which is suitable for production and repeated drilling work, suitable for drilling wood or walls.