Quantity: 8 pieces + a hex wrench Different sizes: 3 mm, 4 mm, 5 mm, 6 mm, 8 mm, 10 mm, 12 mm and 16 mm. The drilling depth stop fits different sizes of drill bits. Carbon steel material: The depth limiter drill bit is made of high-quality carbon steel, with a black surface, rust and corrosion resistance, high hardness, and is not easy to wear and deform. Depth limiter: It is mainly used to fix the limit drilling depth on the drill bit and accurately control the drilling depth. Fixed in place, the screw ring will not damage the drill. Easy to use: Simply choose the right size drill bit and stop ring, slide the stop ring onto the drill, set the desired depth with a ruler or depth gauge, and then tighten the ring screw onto the drill.Good quality product