TECHNIKS 5/16" SUPER PRECISION ER20 COLLET .0002 ACCURACY CNC CHUCK MILL Our Part # TEC-04220-5/16 The most accurate ER20 collet in the industry- average 0.0002 Total Indicated Runout (T.I.R.) Clamping Range .273-.312 Precision ground and hand inspected. Only the very best materials and grinding techniques used