Mattress cover sheet is made of soft cotton fabric. The tone is soft, easy to wear and holds well. The jumbled rubber does not let the flask float off the mattress and it stays on the mattress. Perfect for mattresses with a thickness of up to 10cm. Made from 100% cotton. Why is cotton used? cotton is free from allergic raw materials and chemicals. Its fibres are more durable and smoother, making the material milder. cotton fabrics have higher airflow, making this material anti-allergic - it does not irritate the baby's delicate skin.