These pajamas run small. I ordered the 12 to 18 month size because our twin boys are 12 months old. Only the smaller if the two boys, who's at the 10th percentile for height and weight, can wear them, and I suspect that will not be for long--like, maybe for another week ir so.  The zipper sometimes sticks a little, too. But, I am still giving them a 3 out of 5 because the fabric is super soft and the feet are grippy. I ordered some pajamas from Old Navy, and the feet are entirely too slippy, and they also have the same sizing issue.