Mechanic for small

This set of "mechanical" features 94 large pieces that can be handled by children from 2 years after the manufacturer, but not before 4/5 years in my opinion. The diagrams provided are fairly simple to make and kids can easily handle the rods, wheels, screws ... However, it is not simple to reproduce the construction scheme without the help of an adult. My 4 year old son and a half plays very little alone, even if he can create his own objects. By cons, my 7 year old son loves; so do not rely on the age indicated by the manufacturer because it takes a certain maturity to imagine and create objects. Minor complaint: the box is cardboard and abyss in time; I would have preferred a barrel to store parts.