I used to make these all the time with "wheat berries" in 100% cotton pleted sacks, so the berries don't shift. I filled each pleat with the berris useing a funnel. They have a shell to them wich makes them durable over many reheatings. I also add whole cloves as aromatherapy. I also made pillow cases for them. 2 minets is nice and warm. If you put it in a gallon freezer bag in the freezer it makes a nice cold pack. (beats defrosting your peas)