Exterior: 97% Rayon Made From Bamboo, 3% Spandex Filling: 100% Polyester Highly breathable J-shaped double zipper The one that started it all: Our silky soft, breathable sleep bag that keeps little ones comfortably warm all night long. This wearable blanket helps your baby fall asleep (and stay asleep), and is designed with a J-shaped double zipper for those middle-of-the-night diaper changes. Crafted from high-quality rayon of bamboo, this award-winning sleep bag is so soft, you’ll have to touch it to believe it.