I like these A LOT.  They are very soft, and the elastic bands seem to be of a high quality.  We have only had them a couple of weeks so far, but they seem durable.  My son is almost 5 years old.  He is around 47 lbs and 46 inches tall, but he has a big bottom.  I bought these in a size 6/8, and they fit great right now.  Based on the fit, though, I think he will outgrow them if he gains a few pounds.  So I might suggest buying up if your little one has a well endowed behind.