Organic cotton. The top and bottom layers are made of 100% organic knit cotton. The middle is a thin layer of 100% polyester fleece to increase the warmth factor. There are no toxic chemicals, making the band safe and secure for your baby. The band is BPA Free, Phthalate Free, Latex Free, Lead Free, Anti-bacterial, and eco-friendly. We use100% organic water-based dyes in all our bands.