Amazon.com: 80/20 Inc., 40-4040, 40 Series 40mm x 40mm Extrusion x 610mm : Industrial & Scientific
40mm x 40mm Lite T-Slotted Aluminum Framing Extrusion - Alufab Inc.
Slot 10 40x40mm Aluminium Extrusion, Lightweight, 4 open slots. Priced per metre - Flowstore
Black 4040 Aluminum Extrusion Profile European Standard Linear Rail 4040 Aluminum Profile Frame Machine DIY 3D Printer Workbench CNC (400mm) 1PCS: Amazon.com: Industrial & Scientific