aden + anais australian muslin sleeping bag - Muslin is a unique cotton fabric first introduced into England in the late 17th century. Muslin has a light, open weave that allows air to flow seamlessly through the material. The soft natural fibers allow your baby's body temperature to adjust naturally, eliminating over-heating, but ensuring warmth and comfort. aden + anais wraps will allow you to safely swaddle your baby, giving you confidence that your baby will experience a peaceful and secure sleep. Sizes: small: up to 6 months (23"-28" height) medium: 6-12 months (26"-31" height) 100% cotton