... material of this kind of hex screw: Grade3.6,4.6,4.8,5.6,6.8,8.8,9.8,10.9,12.9,etcCarbon ... plating Light oil,spray coating,electrophoretic coating,etc Polishing Grinding and polishing,etc,except mirror finish (3),Ability for the tolerance ... to supply you the high quality products with lowest price and delivery on time as we can .We have abundant experience ...