TECHNIKS 3/8" SUPER PRECISION ER40 COLLET .0002 ACCURACY CNC CHUCK MILL Our Part # TEC-04240-3/8 The most accurate ER40 collet in the industry- average 0.0002 Total Indicated Runout (T.I.R.) Clamping Range .336-.375 Precision ground and hand inspected. Only the very best materials and grinding techniques used