TECHNIKS 12.0 MM SUPER PRECISION ER20 COLLET .0002 ACCURACY METRIC CHUCK Our Part # TEC-04220-12 The most accurate ER20 collet in the industry- average 0.0002 Total Indicated Runout (T.I.R.) Clamping Range .433-.472 Precision ground and hand inspected. Only the very best materials and grinding techniques used