The positioning ring is an accessory to down-thrust clamps 23310.0050 - .0058 and 23310.0070.
After aligning the clamp positioning rings are fitted on the spindle with the effect that repeated clamping is always exactly on the same point. Positioning ring is rotating by 360° on down-thrust clamps. After mounting the clamp can swing 110° to the left or right.
Before mounting the positioning ring, pull-off top portion of down-thrust clamp.