L size, 6-12 months Because it's a foreign size, it felt a little big. I wore it twice as swim pants. I'm selling it because my child quickly outgrew it. It had a cute pattern, so I'm offering it for sale. Product Description: Happy Nappy is swim pants with a diaper function. Therefore, disposable swim diapers are unnecessary. Made with wetsuit material, these reusable swim pants are recommended by over 90% of swimming schools in the UK due to their excellent functionality.