PREMIUM POLYESTER/RAYON BLEND – Boasting three layers of buttery knit fabric for superior softness and stretch, our three-layer sleep bags are designed with baby’s comfort in mind. That’s why we created them with ultra-soft, breathable fabric with just the right hint of stretch. You can feel confident that baby will feel cozy and comfortable snuggled in this special sleep bag as the safest alternative to using loose blankets. These sleep bags are made from the same ultra-soft and stretchy material as our original knit swaddle blankets.