Series, combination of series and method to produce sports shoes of different size, in which each sports shoe of different size comprises a casing substantially rigid and defining an internal compartment for containing the user's foot, a sole associated below the casing and an inner boot disposed in the internal compartment, in order to make putting the foot into the casing more comfortable. The sole has always the same length for all the sports shoes, and the casing has a different size to each other so as to define, on each occasion, an internal compartment with a different volume for each of the sports shoes of different size, so as to cover a plurality of foot sizes, within a determinate range, keeping the length of the sole always the same.