A friend of mine makes and sells these as sets (literally sells hundreds of them each year!). She has tried several options and sticks with the 2 sides of cotton and the ALL COTTON thin batting. This turns and topstitches the easiest. She does include a little card with them that says for 'reheating, should not be used for more than 4 minutes in microwave'. We actually use it for a bit longer, but this is a safety margin. My kids also love them for holding their ice cream bowls! REMINDER - make sure you are getting the all cotton batting (some say cotton and when you look closely it says 90% cotton), fabric and thread. Polyester does not do well in the microwave!!!