Metalized mylar is layered between polyester fleece to create a high-quality barrier that reflects* heat or cold. This special combination of materials is very flexible and easy to sew through. Once you have sewn it into your project, you can machine wash, tumble dry, and iron with no bunching (low to medium heat settings are recommended). A handy 3/4-yard cut is enough for a large lunch bag or several potholders.