New, genuine MRE ration heaters. You get one sealed pack of 12 heaters.
These are old stock (as in 1992) but still work great. They take just a little longer to get going than the newer ones but these things have a 60 year shelf life.
Just add a little water, lay them flat and let sit for about five minutes and once they react they get so hot they are hard to hold.
These sell for $1.50-$1.95 per heater elsewhere.
We had a one time buy on them and once they are gone they are gone.