ZEN SACK CLASSIC SOLID, POWDER BLUE Size M (6-15 months), 7-12 kg. Help your baby sleep longer - Gently weighted Zen Sack mimics the pressure your baby feels when held by you. Helping babies to self soothe & sleep through the night when not in your arms. Parents report longer sleep in 1-3 nights. Sleep sack has a name stamp on it that can be blacked out or will fade over time. See photo. Questions? Leave a comment below!