AccusizeTools - 4 mm to 26mm by 1mm ER-40 Collet 23 Pcs/Set in Fitted Strong Alu Box, 3350-0586 Size from 4 mm to 26 mm by 1 mm. Range of 0.039''. Total 23 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