SK10 Lyndex Slim Style BT30 Collet Chuck ~ Runout is <= 5 Micron at 4D. ~ BT-30 style has a M12 X 1.75 drawbar end. ~ Dual contacts of taper and flange. ~ Increases spindle contact by 53% over standard holders. ~ Prevent tools from pulling into spindle. ~ Balanced to 30,000 RPM.