Espresso is usually derived from a certain type of coffee bean; Coffea arabica commonly known as Arabica, but the other variety, Robusta, is also used in some espresso blends. Arabica beans are considered to be superior to the more common Caffea canephora (known as Robusta, which are typically used for filler in commercial drip brew coffee, due to their lower level of caffeine and acidity, and their higher amounts of flavor and aroma. The roast of the beans varies from dark to light, depending on the desired taste. For making espresso, the beans are ground very finely, unlike coarser drip-style grounds.