【Various sizes】 Drill depth stops of 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm and 16mm will fit drills of different sizes. 【Carbon steel material】 Drill bit Depth Stopper Made of high quality carbon steel, the surface is blackened, resistant to rust and corrosion, high hardness, not easy to wear and deform. 【Depth stopper】 The is mainly used to fix the ultimate drilling depth on the bit and precisely control the drilling depth.Attached securely to the position where they are placed, the screw collar will not damage the drill bit . 【Easy to Use】 Simply choose the appropriate size drill bit and stop collar, slide the collar over the drill bit and set the required depth using a ruler or depth gauge , then tighten the collar screw on the bit. 【Guarantee】 If you have any questions during the purchase and use process, please feel free to email us and we will get back to you within 24 hours