My boys are aged 3 and 5 and I bought them the age 5-6 thermal layer base set (thinking the smaller one will grow into it). Loved the snuggly warmth of it, but my issue is that the waist band seems way too tight. My boys are very lean, but both complained it hurt their tummies. The younger one just won't wear it at all, and the older one will wear it for outdoor football but can't wait to get the trousers off as they hurt him. Shame. Tops are great though!