Shank of Ø 10 mm, or 13 x 30 mm. With 4 attachment screws (120°offset) for fi xing. Solid quality. The shank of Ø 13 mm has 3 clamping surfaces. For the extension of all cylinder boring bits or all tools with Ø of shank 8, 10, 12, 13 mm. Perfect for drilling deep holes, also for turnery. When ordering, please pay attention the I-Ø dimension.