Patented, fully automatically technic as well as optimal and secure power transfer for an easily manoeuvring of caravans and trailers with tandem axle. Large engaging way and innovative driving roller surface for a safe manoeuvring and a small turning circle. Less weight because of the special mix of materials. The particular engage mechanism with high-performance plain bearings makes the coupling easy at a minimum loss of ground clearance. Technical details: Automatical one-hand operation, climbing power 12% at 3.100 kg respectively 20 % at 1.800 kg, power consumption at the level approx. 40 A, weight approx. 68 kg, warranty: 5 years