I used leftover fleece because it's soft and cuddly. I filled each bag with rice and tested that they work well right out of the freezer (stored in a zip lock bag) and after a quick 30-sec trip to the microwave.
Each kid got a pair of them, one for the freezer and the other for the microwave.
Ironically enough, my daughter had a belly ache tonight and was able to test the warm one. She said it felt really good on her tummy. Success!
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