My grandson wears size 7 Small in other Under Armour clothes. He loved the colors and looks great in this orange and blue swim trunk and shirt set but his measurements indicate he should actually be wearing size XS 4 ,5, or even 6 not a 7 Under Armour Boys' UA Volley Set. We found on multiple size charts on the UA website listings at Amazon there are different size guides. My grandson measures: Chest 24.5" Waist 21.5 " Hips 24". It fits fine and is loose but there is no room to spare in the waist or shoulders. We ordered the UA Volley swim trunk size S located at a different Amazon link to compare with this set in size 7 . On that different Volley swim trunk chart, size 7 would qualify as an XS. We wonder if the lengths will be the same or different, but haven't received them yet to compare. Length is fine for this slim seven year old boy in the size 7 . IT is very good quality, durable for an active kid who needs his clothes to hold up in frequent washings and wearings. Thankful for Amazon because we are going though so many pairs of different clothes just to find the ones that fit. We are trying some clothes using the Amazon Try Now for $0 and Pay in 7 days if we decide to keep.