... /carbon steel, brass, aluminium 3.zinc plated,hdg,black carriage bolt Itemcarriage boltMaterial of carriage boltCarbon steel(,Q235,C1010,C1020,C1040 ... ,10b21,etc)Brass/copper(H62,H65,H68,etc)stainless steel (ss304 ss316,A2-70,A4-70,A4-80)Grade of carriage ...