... testing of hardness, salt spray test, coating and so on.SPECIFICATION:MATERIAL: LOW CARBON STEEL, C1045, AND OTHER MATERIAL REQUIRED BY ... AFTER ORDER PLACED.WE ARE ALSO SPECIALIZED IN MAKING VARIOUS HINGES, IF YOU HAVE ANY SPECIAL REQUIREMENTS OF MATERIAL, FINISH, HARDNESS ... THE DETAIL OR PRINTS. HOPING WE CAN HAVE THE CHANCE TO WORK WITH YOU. Special V shaped Metal hinges