Step drill bits with a triple-flute design for improved stability and reduced deviation during cutting. The 'C-profile' ensures smoother operation and doubles cutting speed. Coated with aluminum titanium nitride for high hardness (89HRC), heat resistance, and durability, outperforming standard black oxide coatings in lab tests. Features 15 step sizes (4-32mm) in a spiral flute design, eliminating the need for multiple bits. Made from M35 cobalt high-speed steel for enhanced hardness and wear resistance, ideal for mild steel, medium-hardness steel, and stainless steel. Color: Black Material: Steel Note: Bag color/style varies by batch. Package includes: 3PCS step drill bits (4-12mm, 4-20mm, 4-32mm). Disclaimer: Slight color variations may occur due to lighting/screen differences. Size tolerance: +/- 1-3cm.