SNOO Sack and SNOO Comforter Sack (our warmer wrap), were specially designed to be used in SNOO Smart Sleeper to help babies sleep safer, longer, and happier! And because SNOO Sack was created by world-renowned pediatrician Dr. Harvey Karp, you can trust that every detail was designed with baby safety and parent sanity in mind! Weight Range Small: 5-12 lb Medium: 12-18 lb Large: 18-26 lb Swaddle Length: Small 20.5 inches, Medium 23 inches, Large 25 inches, Please Note: Don’t worry if your baby’s feet can touch the bottom of the sack. That keeps the legs slightly bent, which aids in developing hips. All three boxes opened but not used. Small, medium and large sacks.