Titanium Coating - Coated with titanium, this step drill set performs well in heat, corrosion and rust resistance. Good Design - Triangle shank fits into power tools chuck securely and eliminates slip; two-flute design clears chips faster and allows particles to escape easily. It can automatically deburr holes while drilling to keep the drill bit clean. This drill bit set includes 3 sizes(4-25mm, 4-30mm,), which meet your different needs perfectly A necessity for family or handyman or professionals - Perfect for home repairs and light jobs such as drilling holes in plastic, aluminum, copper and many other types of sheet metal.