This helmet fits my 24 mth old perfectly, due to the adjustable screwing mechanism at the back. I tightened it to fit her snugly. She is also happy to wear it, being that it's pink with bunnies on it! I feel better about putting her up on her big tricycle now - very safe. All the others we tried on in the stores were far too big. I believe my child's head circumference runs in the 50th percentile. Worth the money for safety's sake.