Use of materials: carbon steel (18A/22A) stainless steel? Copper Surface treatment: zinc, nickel, copper, black phosphorus, TTP (pizza first cross hole) JJ-023 THX (DIN 7976 Hexagon head) JJ-024Use of materials: carbon steel (18A/22A) stainless steel? CopperSurface treatment: zinc, nickel, copper, black phosphorus, Gray P, Lu Po rust, gray (stainless steel, copper) Self-drilling screws