your mileage may vary, and they may change how they are made. But in our experience in January the "Small" size fits adult bands better than the large size. They are stretchy material and just stretch on. The small size fits snugly, the large size was saggy. Of course the small size fits child sized bands better. If I was splitting a three-pack between adults and children i wouldn't hesitate to buy the small size.
Wait. Those are different than what we got in January. The ones we got stretch over, those look more like stick on.