I ordered this hat for my preemie son, who's now fitting in newborn sizes. It is pretty big on him now, but will probably fit soon. I would say it closer to a "6 month" size than "0 months" or "Newborn". These hats are extremely well constructed and cute. They do not stretch out throughout the day, like some other baby hats and stay on babies head well. I have another Zutano knit hat in size 0-3 and that is a more appropriate fit for a newborn, in my opinion.My son is huge. 5 months, 21lbs and wearing a size 18month. Everything he has is 18-24 and since his head is off the charts I figured this size would work, not so much. I even measured but this hat is way too big. He will grow into it, but for now its too big for his massive head for his age. go figure!Its very cute red and white stripe beanie. Washes up greatI thought this was a very cute nightgown but was disappointed with the size. I had an 8lb 3oz baby boy and he never got to wear this outfit. The hat is also very small. I would not recommend buying this outfit unless you know you are having a small baby.I'm giving this as a gift so other than saying it is so very cute and the fabric is very soft, I can not comment on whether the size is accurate or how it will hold up after a washing or two. My first impression is that it is small, but we shall see.My little guy is only 2 and 1/2 months old, but he's a chunker! He still loves to be swaddled at night and even wear a hat. I got this for our camping trips that we take and it's perfect! Not too heavy or thick. It works out great for the cooler nights outdoors! And we love orange! I was very please with the material, it is soft and stretchy and the size worked out great for him!My toddler is 15 months old. His head measures around 45th percentile for his age. Based on what I could decipher from a previous review, I ordered this hat in the 18-24 month size. It fits with room to grow. We are experiencing a winter-like spring, so this is perfect. His little red candy stripe hat covers his head down to the brows, nape, and well over both ears. I am a happy customer.Super cute hat! Smooth cotton with a bit of stretch. As other reviewers mentioned, it fits very small so make sure to measure your baby's head and look on the size chart. Don't go by age at all. My 6mo with average size head could only fit into 12-18mo size hat.I needed a hat for our 11mo, just to keep his head covered in the carrier or stroller. It's often windy and damp here, but not nearly cold enough for a proper wool hat. This perfect. Enough room to grow; he's off the charts for both height and weight, so I got the biggest available at the time. All cotton, and lovely and stretchy.