http://www.amazom.com/shops/earthwide This is a step drill bit that drills the exact hole you require every time.Minimum fuss when drilling through a wide range of materials.The hole diameters range from 4mm right through to 32mm in 2mm increments.Most people use the step drill bits for metal yet laminates,perspex,fiberglass,copper,brass,as well as stainless steel and steel are all good to drill using this quality step drill.The high speed steel this is made from is further hardened by a titanium coating that ensures a longer life and being less prone to dulling.