Made of healthy ,food grade non-toxic silicone material,not easily to damage or deform,durable for long time us. It can keep food fresh for long time,different sizes fit most of bowls. Very good elasticity,can be stretched 2 times than the original size. Resistant to heat up to 230?,?can put it in boiling water to wash,also it is cold resistant which can be used under-40?. Can be used in refrigerators,microwave or ovens,easy to clean and it is reusable.