The tag says the size is for a 2-3 year old, but I shrunk it down a bit. Depending on the size of diaper you pull it over it could work for any size baby between 4 to 18 months. I used it over a Happy Heiny pocket diaper for night time only. No stains- it was never pooped in. Only used for a few months, some pilling, but otherwise fabulous condition.