Bosch TI21 21-Piece Titanium-Coated Drill Bit Set Super-hard titanium coating lasts up to six times longer than high-speed steel Self-starting point starts on contact Balanced double flute eliminates chatter and vibration Titanium reduces heat for longer life Drills clean, accurate holes in these thin materials (up to 1/8 In.): sheet metal, ducts, steel, copper, brass, aluminum, plastic, plexiglass, wood, veneers, vinyl siding, plasterboard, PVC, stainless steel and cast iron