AccusizeTools - 12 Pcs ER-20 Collet Sets Holding End Mills, Size from 1/16'' to 1/2'' in Fitted Strong Alu Box, 0223-0799 12 Pcs ER20 chucks set includes the following collet sizes: 1/16'', 3/32'', 1/8'', 3/16'', 7/32'', 1/4'', 5/16'', 11/32'', 3/8'', 13/32'', 7/16'', 1/2'' Concentricity: 0.0004'' Design affords highest gripping power True double angle fo better accuracy For powerful gripping and parallel clamping