Feature 1Hollow drill bit's teeth can be not easy to break depends on that it keeps silver welding technology to weld firmly. 2Even force and smooth cutting keeps that three blades are stressed at the same time. 3Not easy to damage, this high‑speed steel drill bit keeps high‑quality and high hardness with wear resistance. 4Drill the depth of up to 50mm, metal hollow core bit can easily solve the thickness below 50mm. 5Suitable for cutting materials such as stainless steel, copper plate, steel plate, aluminum plate, etc. Item Type: Hollow drill bit Color: SilverMaterial: High speed steelSize: (Approx. 20 x 50mm / 0.79 x 1.97in) / (Approx.21 x 50mm / 0.8 x 2in) / (Approx.22 x 50mm / 0.9 x 2in) (optional)Size1: Approx. 20 x 50mm / 0.79 x 1.97inDiameter: Approx. 20mm / 0.79inDepth: Approx. 50mm / 1.97inShank Diameter: Approx. 19mm / 0.75inInner Hole: Approx. 12mm / 0.47inSize2: Approx.21 x 50mm / 0.8 x 2inDiameter: Approx. 21mm / 0.83inDepth: Approx. 50mm / 1.97inShank Diameter: Approx. 19mm / 0.75inInner Hole: Approx. 13mm / 0.51inSize3: Approx.22 x 50mm / 0.9 x 2inDiameter: Approx. 22mm / 0.87inDepth: Approx. 50mm / 1.97inShank Diameter: Approx. 19mm / 0.75inInner Hole: Approx. 14mm / 0.55inApplication: Suitable for cutting materials such as stainless steel, copper plate, steel plate, aluminum plate, etc. Package List 1 x Hollow Drill Bit