Many people choose to make apple cider vinegar a gallon at a time, but you don't have to. You can use any size mason jar. I prefer to use glass jars that are about a pint in size. This allows me to make smaller batches that are ready to be pulled as needed. I don't use a gallon at a time because it's more difficult to store and manage a large batch. If you're new to making apple cider vinegar, I suggest starting with a smaller batch so you can get a feel for the process and decide how much you need to make at one time.