... internal thread and castle screw Ability for the material of this kind of nut: Grade3.6,4.6,4.8,5.6,6.8,8 ... while,colour,dacroment),Nickel plated,copper plated,gold plated,chrome(3+Rohs &6+ ) plated,anodic oxidation,etc Dip plating black oxide ... plating Light oil,spray coating,electrophoretic coating,etc Polishing Grinding and polishing,etc,except mirror finishAbility for the tolerance: Roundess0. ...