Size Medium for 6-12 months. Dreamland's patent-pending Dream Weighted Sleep Sack is designed to help your baby feel calm, fall asleep faster, and stay asleep longer. The sack features our exclusive CoverCalm® Technology, evenly distributed weight from your baby’s shoulders to toes to naturally reduce stress and give your baby the feeling of security and comfort - just like a hug. This sleep sack is a 1.0 TOG, perfect for 68-73°F or 21-23°C. Zips down middle and bottom.