Size from 3 mm to 20 mm by 1 mm. Range of 0.039''. Total 18 ps/set. Made from alloy spring steel and hardened to HRC 44-48 All collets are checked its runout individually on 4 points on a testing rod For size 3.0mm and larger the runout is 0.0003'' (0.008mm). Under size 3.0mm the runout is 0.00059'' (0.015mm). In fitted strong Aluminium Box Metric ER Collet 3mm to 20mm by 1mm ER-32 Collet 18 Pcs/Set in Fitted Strong Aluminium Box, #3350-0585 Size from 3 mm to 20 mm by 1 mm Total 18 ps/set Range of 0.039'' Made from alloy spring steel and hardened to HRC 44-48 All collets are checked its runout individually on 4 points on a testing rod For size 3.0mm and larger the runout is 0.0003'' (0.008mm) Under size 3.0mm the runout is 0.00059'' (0.015mm) In fitted strong Aluminium Box