Children’s one size fits most. My son wore it in third or fourth grade and it was slightly big but definitely doable. Has a battery pack that inflates the costume after you put it on. The head comes off and the rest will stay Inflated. This was great for two reasons- first my kids school did a costume parade but masks that covered the face weren’t allowed. So he wore the body, and we bought a chef hat to wear on his head! I could include that with the costume if you want. Second, he got tired of wearing the head part while trick or treating so he took it off after a while!