Waist: 47cm-65cm (18.5"-25.59") The product is very adjustable, so a one size fits all for the most part.
It's important that kids get a good posture while they're young. This way they get the muscle memory while they are young. It'll become a habit for them. If you wait then you'll end up with someone with much more permanent posture issues, as well as more expensive ways to help correct it. This posture corrector is here to get these problems fixed now. This back brace is the best one we could find from any supplier that had such good ratings and wasn't hundreds of dollars.