They come in different sizes and thicknesses. I would go for at least a medium thickness. I do use a crimper made especially for mylar, but I know people who do use a regular iron with success. If you plan on getting into the food that you sealed in a bag, then the zip lock mylar might be a way to go. But you'll pay more for it. Some use the huge mylar in a 5 gallon bucket to store a lot of rice, for instance. I don't like to open up that much at a time, so I use the 8 x 10 inch bags, then put them in a bucket or bin. Include oxygen absorbers in your order, but don't use them for sugar or salt. Remember, mylar is not rodent proof, so even if food is sealed in them, put them in a sealed bin or bucket. I use the meals in a jar recipes and bag them in mylar for quick grab convenience meals. Do enough of them and you'll have meals for a year.