Love to Swaddle UP is the original & innovative swaddle that allows your baby to sleep in their natural position, with their arms up. The small size is for 6.5 - 13 lbs. Arms up in wing position helps prevent your baby rolling onto their tummy. Helps self-soothe and sleep longer. Helps calm startle reflex. Trans-seasonal cotton spandex fabric helps prevent overheating. Snug fit helps prevent tangling and fabric riding up over your baby's face (helping prevent the risk of SIDS). Genius twin zipper means no unwrapping for diaper changes or transporting from carseat to crib. The Light is 30% lighter for warm months.