Right Size → Sleep Better: Use baby's weight to select sizes. ZIGJOY Shark-Fin sleep sack is available in 2 sizes. SIZE MEDIUM fits for babies weight 10-18 lbs, aged 3-6 months, and height 23-27 in. SIZE LARGE fits for babies weight 18-24 lbs, aged 6-12 months, and height 27-31 in.Please refer to the size chart to confirm weight and height. The right size will ensure comfortable snug, proper neckline and good hip movement, promise a secure and cozy embrace for every stage 1.0 Tog, Super Soft, 100% Cotton: Transitional Swaddle is made of 100% cotton, natural and skin-friendly. Safe and Breathable fabric can directly contact with baby's sensitive skin, let them feel very comfortable. It has strong resilience and wear-resistance, durable to use and will not be deformed after washing frequently. Tog 1.0, for room 68-75°F/20-24°C, available for all seasons. Super easy care: machine washable, saving time Great Transitional Swaddle: Transition sleep sack with sleeves acts as a safe wearable blanket in instead of traditional swaddle, preventing baby from breaking out or getting covered/tangled in loose blankets. Special full sleeves allow baby to soothe himself by sucking his fingers with no constriction, and prevent him from scratching himself in sleep. Perfect swaddles for newborn or infants who are starting to roll over Promote Self-Soothing, Help Independent Sleeping: Baby swaddle blanket with tightened waist can wrap and fit the baby well, bring gentle closed feeling of security and effectively soothe them, reducing times the baby wakes up, both parents and babies can sleep better. Upgraded high-quality SBS 2-Way zipper, smoother and not easy to damage, so you can rest assured that you can use it. Easy to put on and take off, change diaper quickly, without affecting baby's sweet dream Widened Hem for Baby's Growth - Roomy hem promotes baby's hip joints development, and legs can kick freely but cannot be kicked off. Baby can stretch fully in this swaddle transition without worrying about limiting their nature. Let the baby grow up happily accompanied by our cute sleep sack swaddle ZIGJOY Shark-Fin Transition Swaddle - Cozy Baby Wearable Blanket Cotton Lightweight Sefl-Soothing Sleep Sack