4 gray coupling rods with springs for fixed connection of vehicles. They reduce the distance between 2 vehicles by about 1.5 mm for a more closed train pattern. Working as a replacement for the "R" type coupling, for 19 and 20 meter chassis. Not recommended for use with 21-meter chassis. When fixing, make sure that the bogies are not twisted and that the tighter coupling allows the cars to run even the tightest radius on your layout.