It's best to choose a Wobble Stool size that allows your child to have their knees and hips at right angles, when both feet are planted on the floor.
You can try measuring from the floor to the top of you child's knee when they are sitting on a chair or something low like a coffee table, and ordering the stool closest to that height (if in between two sizes then choose the taller stool).
A wobble stool is designed to give just enough wobble and wiggle to keep kids moving without being distracting to other's around them.
The wobble stool movement gives vestibular input, as well as proprioceptive input. Both of which can be very calming and meet sensory seekers needs. It helps them listen, concentrate, learn, or do whatever task they are trying to set their mind to ❤
It helps them to regulate themselves and the more we can create little opportunities for that throughout the day the better 😍