My 4 year old needed an elastic so he could put his large pants on and off quickly. The instructions say to order the belt the same size as his waist, so I ordered a size 21. When it arrived and tried it on my son, the belt was exactly the same size as his waist! If I wanted it to fit properly I would have to pull it too tight and tie it around his waist, defeating my purpose. So I returned it. However, as I like the style of the belt and the fact that it stretches, I just ordered it up a size.