The 2 liter (or 2000 mL) flask is a great all around flask for yeast starters, as it can be used in 5 gallon and some 10 gallon batches. If you want to get your starter wort up to a boil using the flask, we recommend you heat it up with a boiling water bath. Place the flask with the desired water amount, into a pot with additional water, and then bring the water up to a boil. Uses a #10 stopper.