Corsair. Mine has buckwheat in it. 2 minutes in the microwave. I also have an old fashioned red “rubber” hot water bottle. It also does a marvelous job. It holds heat much longer than anything else.
Cinnamon Grammy – my concern with the huge stash of thread is that it eventually gets dried out and brittle. I was keeping mine in the freezer but it got “evicted” in favor of berries. Haven’t figured out any new solutions.