We are a one size fits all band. The band is 27.8cm long. The metal housing of the band is (H) 1.0cm x (W) 1.8cm x (L) 3.8cm.
As for whether or not the band fits children, it depends on the size of your child's wrist. If your child's wrist is at least 3.8cm wide, then it should fit when pulled to the last hole on the strap. What we suggest is that if you order one and it doesn't fit, you can always return free of cost.
The effectiveness of Immutouch has two parts, (1) can it detect when a child touches their face, and (2) will the child therefore stop touching their face and build a habit not to touch their face.
For the first point, yes, Immutouch can detect when a child touches their face. But for the second point, it comes down to if you think your child would deliberately stop touching their face at the onset of a vibration. If you think they will, then Immutouch will be effective for your child. But if you think they would just ignore the vibration, then this product won't be effective.