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 &# 39 ; 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 .