Ergobaby Sleeping Bags are made of soft, 100% premium cotton. Our Cozy Sleeping Bags have an additional internal layer of Polyester batting for added warmth.As baby learns to stand and walk, it’s important to enable the freedom for them to do so. The feet openings allow for greater mobility, so baby is free to stand, crawl, or walk about while still wearing their cozy sleeping bag.TOG stands for Thermal Overall Grade. It is a unit of measurement used to calculate the thermal insulation of a product, commonly used in the textile industry (quilts, duvets, and comforters). It indicates the degree of warmth you should expect from your sleep bag. The higher the TOG, the warmer the sleep bag.