A set with which to build a compacting crane and 9 other construction machinery models with over 200 interchangeable components including: flat and bevel gear wheels, rack, differential, worm screw, notched tires, bars and panels. the ru bucket lifts up thanks to the worm mechanism and the car really moves by turning the steering. the illustrated manual accompanies the child in the construction of the models and brings him closer to the principles of mechanics and engineering. and with the free app many other applications to discover and build