20-4040 40mm X 40mm T-Slotted Profile - Eight Open T-Slots

What size T-slot nutsbolts do I want to get for the 20x20 Aluminum 4040 t slot 4040 LIGHT T Slot Aluminum Profile 4040 t slot aluminium extrusion 40mm x 40mm Very Light Tslot Extrusion w 8mm tslot, stick length 6 meters

4040 v slot Oxide Black T-SLOT ALUMINUM EXTRUSION FRAMING 40 SERIES CLEAR ANODIZE FINISH material : Aluminium alloy