This chapter is deliberately short.
The size is measured by the distance between the ground and the top of the withers. It is correlated with the magnitude of the stride but not quite significantly so that we can define an ideal size.
Jappeloup and Milton were rivals with almost 15 cm gap size at the withers. The podium of the Beijing Olympic Games consisted of three small horses.
Small cheetah has a larger stride than rhinoceros, etc...
It is the amplitude of the stride and the ability of the horse to quickly vary the amplitude at the request of the rider which are decisive in this functional aspect of the size.
However, for commercial reasons, we might prefer a "minimum size" and this criterion will be taken into account by the PAX program to analyze the compatibility of the proposed crossings points. Dressage and CCE to high-level do not welcome "small" horses.
If this criterion is irrelevant in the eyes of the breeder, they simply do not check it on the characterization document and it will be neutralized in the operation of the program.