I love these shirts. I bought these for my third baby, I had saved most of the clothes from the previous kids, but all of the onesies were short sleeved. Being that it was too cold for a baby to wear short sleeves all the time, I opted to buy these so I would have the option of putting it on over the short sleeve onesie. They are awesome. Easy to get on and off, not too thick and heavy, but warm enough that another layer was hardly ever needed. I bought the one size-6 months, and my baby has worn them from about 2 months old to now 5 months old, and still has room to grow. When she does outgrow these, I will be ordering the next size because they work so well for us.