These Muslin Sleeping Bags from Aden + Anais offer a warm and cozy night"s sleep for baby. Made from the same breathable, 100% cotton muslin used for swaddling newborn babies. Composed of a single layer of waffled cotton, these quilted sleeping bags provide a layer of cushiony warmth produced from only the most natural of fibers allowing babies and toddlers to stay snug without overheating. Easily fits over pajamas and has a zipper for effortless on and offs.