The tie rods with the special Allen nut are suitable for the linking of a number of valves one above another. They simplify assembly work because they can be manufactured in any desired length. Standard lengths manufactured up to 1 m (greater lengths possible on request). The Allen nuts are special nuts with a female thread and Allen head. Their external diameter corresponds with that of the head of an Allen screw. By reason of the special manufacturing method employed the tie rods have the quality grade 10.9. The Allen nuts have the quality grade 10.