Size S (3-6 months, 12-18 pounds). New & never used but tags removed for washing. I also have size L listed for sale and happy to bundle them! The sleepsuit is designed to help your little one when breaking out of the swaddle but still seeking the safe and comfortable feeling that the swaddle provides. The Magic Sleepsuit provides that cozy feeling while allowing your baby the freedom of movement they need as they develop. The Magic Sleepsuit is designed to be used in accordance with the Safe Sleep Guidelines including the ABCs of sleep (Alone, Back, Crib) and in a room at the AAP recommended temperature for babies, which is on the cooler side. Proper fit and the timing are the most important factors in the use and success of the Magic Sleepsuit.