I use cracked corn that they use to feed animals, keep it in a zip-lock bag in freezer to be ready for unexpected bumps/aches. easily warmed in the microwave if heat is needed, just take out of the bag first. I also made removable flannel case/covers for them that I could just throw into the washing machine when needed. I have one that I heat up to use for my cold feet when I go to bed. (dog loves it too) It warms the bed up nicely in the winter. Common sense says do not make it HOT!