1.Surface:black,phosphated,galvanized.. 2.Grade:4.8,8.8,10.9, ... steel,45# steel,40Cr,42CrMo high strength hex bolt, hex cap bolt, balck bolt1. Surface:black oxide, phosphated,galvanized, Dacrotized 2. Grade:4.8, 8 ... quality control(3) very reasonable and competitive price high strength black bolt