I-Beams 1418 8pcs 20x28 Angle Bracket Right Angle 2020 Series Connector 2 Hole Aluminum Bracket for Aluminum Extrusion Profile with Slot 6mm 20 x 28 x 28 mm (0.78 in x 1.1 in x 1.1 in); Fits most metric 20 mm x 20 mm series aluminum extruded rails.