After the swaddle stage we were looking for something cozy and safe to keep our baby in during sleep time. I looked at a lot of sleep sacks and decided it was important to get something that was made out of all natural materials, no polyester lining or fill. Made from 100% merino wool and 100% organic cotton, the Woolino 4 Season Baby Sleep Bag is an amazing sleep sack and I think an essential purchase for a new baby (or also of course if you already have a baby). This is a four season sleep sack that lasts from 2-24 months, so baby can wear it year round. Both of these factors make the higher cost (higher than a synthetic sleep sack) more economical in the long run.