Stella McCartney swimwear set (top and bottom) However, the sizes are different. Top: 2 years old Bottom: 9 months old Used only about 4 times, once or twice a year, and is in good condition. As this is a used item, please check the photos and purchase only if you understand. The bottoms seem to be made a little larger so they can be worn over diapers. This is just my personal opinion. My child, who was around the middle of the growth curve in terms of weight, was able to wear them at 3 years old. Since her legs, bottom, and stomach area were relatively slim, please consider this as a reference. It may not apply to your children, so please consider the size carefully before purchasing. At 3 years old, she may have worn them without a diaper. Of course, there were no accidents, but please refrain from purchasing if you are concerned. There is no particular stretching. Please feel free to ask if you have any questions.