When purchasing 6 pieces and one piece (unused 2 pieces) is tightened, the screw becomes stupid and the screw does not tighten. There was a defective product. Screws can not be used in places where they are too strong and need strong strength. Indeed, absolutely can not be used in places like human life! It is! Since our company is a screw shop, we know the sides well. Products like synonyms of cheap ornaments.