We bought two of these in 6 to 12 months for our twin boys. While we really like the product design and quality we are very disappointed to find that it is not true to size.
When we got the product the boys were 7 months old and the sleepers fit well. Now, at 8 month they are tight around the chest and barely long enough. The biggest drawback though is that the sleeves are not wide enough, the hands no longer fit through so that we can't use the sleepers anymore, after owning them for only 3 weeks.