ISO 15488-C (DIN 6499-C), for collets ER DIN 6499-B, with SK shank according to ISO 7388-1 (DIN 69871), hardened surface HRc 58±2, with a tensile strength in the core of min. 950 N/mm², tolerance AT3, integrated run-out of 0.005 mm, balanced G6.3 at 15000 rpm, incl. collet Nut