Happiest Baby Snoo Sack bundle, Size Medium 12-18 lbs. Ivory, Size Medium. Midnight Planets, Size Medium. Washed once, never used. No stains or holes. SNOO Sleep Sack is the ultra-soft, ultra-easy swaddle sack that helps babies be happier and sleep longer—and it’s the only sleep sack that should be used with SNOO! SNOO Sack has special wings that slip onto SNOO’s clips to secure babies on their backs and prevent risky rolling. This award-winning swaddle sack was created by Dr. Harvey Karp, America’s most celebrated pediatrician. Dr. Karp is the doctor whose 5 S’s started the Swaddle Revolution, so parents can rest easy knowing he designed every detail of SNOO Sleep Sack with baby safety—and parent sanity—in mind.