Premium natural fabrics Silky-soft hypoallergenic merino wool lining and the finest organic cotton outer. 4 Season use Unlike other brand sleep sacks that come in either winter or summer weight/TOG rating, the Woolino 4 Season Sleep Bag can be used year-round. It’s suitable for room temperature 63-75F (17-24C). Because of merino’s unique ability to regulate body temperature, it helps keep your baby warm when it's cold and cool when it's hot. Grows with your baby It has a universal size so it can be used for babies 2 months up to 2 years old. For smaller babies, simply close the underarm snaps to adjust the fit. Excellent value You don’t have to buy a different sleep bag every few months. Woolino Ultimate 4-Season Sleep Bag is the only baby sleep bag your baby needs, in winter or summer, until they turn two years old. Designed to be practical It features double shoulder snaps and a two-way side zipper, so it opens up completely flat for easy dressing without waking the baby. For easy nighttime diaper changes, you can open the bottom only. Zipper-pull guards protect baby's skin and discourage baby from chewing on the zipper pull. Travel friendly A closable seatbelt opening allows for easy transfer between stroller, car seat, and crib, so you can keep your baby’s sleep routine intact while on the go. A safer alternative to loose blankets Helps your baby stay covered through the night, replaces loose blankets in the crib, and promotes back sleeping.