RUKO Drill Bits & Parts Step drill bit set 616460 - RUKO 101352, Ruko manufactures the 101352 Step Drill Bit Set, known for its high-speed steel construction and triangular shank. Designed for quick drilling in sheet metal, the set includes three bits ranging from 4 to 30 mm. This tool is ideal for creating precise holes in various metal materials. RUKO 101352 Step Drill Bit Set 3-Piece 4-30mm HSS Triangular Shank