Boeray 4 pcs Zinc Alloy Door Frame Hinges for Combining 3030 and 4040 Aluminum Extrusion Profile Slot 8mm Material: High quality zinc alloy Finish:Electrophoresis processing of electronic industry, anti-corrosion. Include: 4 pack-4pcs Zinc Alloy HingesCombine 3030 Aluminum Extrusion Profile slot 8mm and 4040 Aluminum Extrusion Profile slot 8mm Widely used for building industrial aluminum frame structures, 3D printers, CNC Routers, CNC laser cutters, Robotics Projects