A non-disposable swim diaper is mandatory for pools when taking swimming lessons typically up to the age of 4. We purchased the Iplay Ultimate Swim Diaper for our son and after a few attempts at sizing, ended up with the 3T size when he had just turned 2. He is tall and slim so I definitely suggest sizing up for your little one! It is snug fitting to keep any accidents contained. The diaper is rated UPF 50+ and all iPlay products are PVC free. We have been very pleased with this swim diaper and will continue to purchase from the iPlay line as our child grows. Check out the iPlay Swim Diaper on Amazon.com!