5.5 oz. Milk peanut butter cup with Lynn, MA Marshmallow Fluff. Marshmallow Fluff has been produced using the same batch process for 100 years and is the only marshmallow creme made this way. It’s what makes Marshmallow Fluff so fluffy, white, smooth and delicious. It’s the key to making our delicious marshmallow peanut butter cup and our S'mores. 6 month shelf life.