Spring steel, through hardened and ground. The through bore (longer clamping range than DIN collets) increases the clamping force. More slits than DIN collets, giving a greater insertion depth in the collet chuck. Suitable for jobber drills, for clamping on the guide land Clamping range = Nominal size down to minus 0.5 mm. 5 or 6 slits each end.
- Better radial run-out = axially parallel centring in taper; no tumbling.
- Higher clamping force = due to improved grip.
- Higher system stiffness = suitable for high-speed milling.