For my 7-year old daughter, the 7/8 (small) size was way too big all around. The XS gives her a little growing room in the waist but can be easily adjusted thanks to the handy velcro straps on either side. The length is just about right for her. Usually that's a no-go for kids clothes that will be used for only 2-3 ski trips per year. But the 2" of extra length offered by the "grow cuffs" makes these a no-brainer. Good for now and for another season or two. And since they're North Face, I expect them to hold up well enough for my 4-year old to wear when the time comes.