These devices are useful for straining purées or thick sauces such as tomato or tomatillo. They are available in different sizes. The smaller sizes are not of much use in a professional kitchen, because it is just as easy to work a small amount of the mixture through a medium-mesh strainer. A large food mill, however, is almost indispensable for straining large amounts of tomato coulis and purée-thickened mixtures. Food mills come with several perforated metal plates that can be switched depending on the desired consistency of the mixture.