High Quality Materials: 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. Several sizes: Depth Stop Drill Set consists of 8 pieces of 3mm, 4mm, 5mm, 6mm, 8, 10mm, 12m, 16mm and small wrenches. Different specifications may meet different needs. Easy to Use: Simply choose the appropriate size drill bit and stop collar, slide the collar over the bit and set the required depth with a ruler or depth gauge (not included), then tighten the collar screw with the drill bit included hex key wrench. Improved Design: The split ring design allows the stop collar to lock securely along the diameter of your bit, Screw bottom collars can cause alignment or damage the bit, but our Improved split ring units have a split design with a face parallel to the axis of the bit and they will not move or come up on the bit after being tightened. Usage: Drill Depth Stops used to precisely control the drilling depth when drilling holes in wood to avoid material waste.