Works for my 6 year old neice. So well in fact that she switched to sucking her other thumb! Her mom is buying her a second one for the other arm. A tad bit pricey when you need two, but considering the orthodontist costs and other oral problem that thumb sucking can lead to down the road, I think it’s a good investment. I looked into cheaper options but I like this one because it doesn’t let them put their thumb in the mouth.
Pros: Works!! Doesn’t interfere with activities. Does not come off.
Cons: A bit pricey when buying two.