These truss rods come in 3 lengths - 440mm, 580mm and 620mm.
Truss rods are used in the production of guitar necks. They were quickly found to be a necessary part of any guitar neck after the first ones made were found to warp under climate changes and consistent high tension of the strings would pull the neck into a bowed shape.
These are 6mm wide and 9mm tall.
7mm diameter x 26mm long nut on the end of 620 and 580mm long rods
6mm diameter x 30mm long nut on the end of 440mm rod.