Container sizes range from "nanos", particularly magnetic nanos, which can be smaller than the tip of a finger and have only enough room to store the log sheet, to 20-liter (5 gallon) buckets or even larger containers, such as entire trucks. The most common cache containers in rural areas are lunch-box-sized plastic storage containers or surplus military ammunition cans. Ammo cans are considered the gold standard of containers because they are very sturdy, waterproof, animal- and fire-resistant, and relatively cheap, and have plenty of room for trade items. Smaller containers are more common in urban areas because they can be more easily hidden.