Use on 40mm x 40mm Extrusion Profile, 4040 Series Aluminum Profile Connector Set widely used for building industrial aluminum frame structures, 3D printers, CNC Routers, CNC laser cutters, Robotics Projects. Aluminum Corner Bracket used to connect pieces of 40mm aluminum extrusion at a 45 degree 135 degree angle suitable for most of metric 40 Series Aluminum Profile Extrusion.