These are my favorite sleep sacks. I got my first one as a present from another veteran mom. Before these I went through a number of different sleep sacks, swaddlers, and sleepers and I found that it was difficult to keep a baby at the right temperature. The fabric of these is breathable. Other sleepsacks weren't and so my baby ended up getting too warm, getting all sweaty, and then getting clammy. Once I realized how much better quality these were I bought several for myself and as shower gifts.