How do I know if my child needs junior bindings or adult XS bindings?

Check the child's snowboard boot size against both the junior and adult binding size charts. If the child's boot fits properly in a junior binding's heel cup with straps able to secure it without bottoming out or excess overhang, stick with junior — the softer flex is more appropriate. Move to adult XS bindings when the child's boot size exceeds the junior binding's range, or when the child rides aggressively enough to benefit from stiffer response that junior bindings can't provide.