This item was worn from 0 years old. It's a year-round material. It was mainly used to protect against the cold from air conditioning. In the summer when my child was 1 year old, they slept restlessly, so instead of using a futon or sleep sack, I only used this belly band. It stretches more than it looks and doesn't feel tight. I think it can be worn for a long time, from newborns to around 5 years old (waist circumference 54cm). Stored at home & home-cleaned. Thank you for your understanding regarding used items.