... cutter for wood in different types on high working efficiency.Diameter for plug(metric):6,8,9,10,12,14 ... ,15,16,20mmDiameter for plug(inch): 1/4", 5/16", 3/ ... "Shank Type: 1/4" Hex Quick Change System or 8mm diameter round straight shankSurface treatment: Bright finished or Black-oxidedHardness: HRC44 ...