Convenient 2-Way Zipper: The double-zipper function not only makes it easy to put on and off, but also allows for quick nappy changes at night without waking the baby. The top zipper protectors prevent any scratches to your baby's skins, ensuring your beloved one safe and comfortable. Tightening Waist for Better Sleep: This sleep sack with arms up brings baby a slight sense of restraint, just like mom's womb makes baby feel familiar and secure. Plus, it reduces your baby's unexpected movements, helping your baby stay asleep in this swaddle. Widened Hem for Hip Healthy: Compared to others, this baby swaddle features wide hem with M-shaped foot design. The scientific M-foot design helps baby's legs maintain natural sleep position. Besides, the large room allows baby to kick or wiggle legs freely, which promotes the development of the baby's legs and hip. Soft and Stretchy Material: ZIGJOY Arms free wearable swaddle is made of 95% cotton and 5% elastane, which is super soft, stretchy, lightweight and velvety to the touch. Tog Rating 1.0 for room temperature 70-73°F/21-23°C. Ideal for year-round comfort, keeping your baby warm but not overheated. Baby Swaddle Sack with Unique Arms Design: Arms design allows babies to sleep in their preferred natural position while a slight sense of enclosure can effectively prevent the startle reflex. In addition, openable arms allow baby to self-soothe by sucking on fingers. As your baby sleeps better, you can get more sleep too.