This works best for my larger baby. He was born in september in Montana so it was already starting to get cold here. We started with the Kiddopotamus SwaddleMe Bamboo Blanket, but it just wasn't warm enough for our cold nights. I had boughten this before he was born in size Medium, which was 3/6 on the tag when it arrive, with the plan to use later in the winter, but started to use it when he was about a month. It works great even though it's a little big. When I first got this I thought it was so long for the size, but when he wears it he fits good. He was a long child though, but if your baby is shorter it would give them plenty of room to grow. It also snaps up on the bottom so if your baby happened to get too long for it you could leave it unsnapped and let their feet hang out. I feel like that would be very unlikley though because this is very long. The double zipper is great for middle of the night changing, and he stays comfortable. If you lived in warmer climats you probably wouldn't want this because it's a very nice fleece on the inside and flannel on the outside...so 2 layers. It also washes up very nicely. I'm sure he will be able to wear this all winter without outgrowing it...and he is a very large baby.