8 sizes: 8 different depth stoppers, the box contains 8 different depth stop rings (3, 4, 5, 6, 8, 10, 12, 16 mm) for different types of drills and hex keys. Sustainability: Carbon Steel Retaining Rings are made of high quality carbon steel for durability and long life. It will precisely control how deep you drill. Wide range of uses: Drill stop ring is suitable for repeated drilling operations, suitable for twist drills, auger drills, angle drills, etc. Can be used to drill wood or drill walls. Premium material: carbon steel retaining ring; center of pin is stainless steel. Wear-resistant and corrosion-resistant, it is a good tool for woodworking and wood crafts. Method: It is mainly used to set the limit drilling depth on the drill bit and precisely control the drilling depth. It is not only suitable for standard drills, but also for elbow drills. The set screw ring will not damage the drill. Material: carbon steel Colour: Black Overall length: M3: Inner diameter: 3mm/0.1 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M4: Inner diameter: 4mm/0.1 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M5: Inner diameter: 5mm/0.2 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M6: Inner diameter: 6mm/0.2 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M8: Inner diameter: 8mm/0.3 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M10: Inner diameter: 10mm/0.4 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M12: Inner diameter: 12mm/0.5 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches M16: Inner diameter: 16mm/0.6 inches, thickness 3mm/0.1 inches, height 8mm/0.3 inches The package includes: 1*M3 1*M4 1*M5 1*M6 1*M8 1*M10 1*M12 1*M16 Only the above package contents, excluding other products.