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 in the mic. is nice and warm I heat it for 2 1/2 but I like it hot that might be too hot for her.