9/18 PCS Depth Stop Drill Bit Collar Set Positioner Ring and Hex Wrench Tighten The Stopper Set Screws Woodworking Tool 9/18 PCS Depth Stop Drill Bit Collar Set Positioner Ring and Hex Wrench Tighten The Stopper Set Screws Woodworking Tool About this item 8 Different Size Drill Stop Set. The diameter of the stop collar are 3mm, 4mm, 5mm, 6mm, 8mm, 10mm, 12mm, 16mm. The diameter of the hexagonal is 2.5 mm. Sturdy Material - These Drill Stop Assortment Set are made of carbon steel, which is durable and sturdy for long term use. They will stay sturdy when tightened and is specially designed not to damage the bits. Usage - Mainly used to fix the drill bit and limit the depth of the drill hole, so that the depth of the hole can be consistent. More convenient use of round tenon. Necessary Tool for Drilling - This Drill Bit Set will help you to control the depth of the hole you are drilling accurately. Advantage - The Positioner Ring can be used on twist drill bits, brad point drills or any types of bit to prevent excessive drill bit penetration. Perfect for any job that requires precision. _x000D_