MATERIAL: High speed steel(SKH51) SIZE RANGES; 12mm-100mm diameter APPLICATIONS: For tough drilling on 1.6mm thick iron plates. USES: (A) Electric work: 1.Electric control box''s push-button hole. 2.Refrigerationg machines. (B)Iron work: 1.Sheet metal work. 2.Drill hole installationg. SPECIAL FEATURES: (A)Sharper teeth tip for easier cutting. (B)Longer product life,teeth stay sharp longer. (C)Better chip clearance. (D)For precision hole drilling. SURFACE TREATMENT: (A) Nickel coated (B)Golden finish (C) Sand blasted (D)Black oxide)