For ages 2m to 24mnths. We have had three of these in different sizes, they are really great. For a baby from 10lb-40lb. Zips and domes mean it can be snug for cooler nights and airy for warmer weather. Zip at the feet means your little one can walk around in it without completely taking it off. Pockets at the front and back allow you to check for a wet diaper without taking it off or disturbing their sleep.