Both kids in the pictures are wearing the size they normally wear in ready to wear (4T for the girl and 2T for the boy). Size down if you want a tighter fit.
Made with a lighter weight french terry that is a poly/rayon/spandex blend for the main fabric and a cotton/spandex ribbing for the cuffs and bands to ensure proper stretch and recovery.
Washing instructions: Machine wash with like colors (no towels, Velcro, or jeans), lay flat to dry. No bleach. If you need to iron, do it on a super low setting.