Diameter: 4.0mm. Suitable for general purpose applications, including: aluminium, copper, iron, mild steel, wood, plastic. High speed steel, roll forged. DIN 338. Pack of 10 also available, Part No. 32908. Part of a range of jobber drill bits in metric & imperial sizes from 1.0mm - 13.0mm (Part Nos. 32900 - 32927) & 1/16" - 1/2" (Part Nos. 32932 - 32960).