Inkjet drop sizes are measured in picolitres. One picolitre is a millionth of a litre. Depending on the printhead configuration, the drop sizes normally range from 3 or 4 picolitres to more than 100 picolitres. Photo-quality printers such as Epson Stylus Pros generally produce the smallest drop sizes, and many of these use greyscale heads that vary the size of drop too. Printers used for signage and similar applications that are viewed from a distance can use larger drops, which cover a given area more quickly to allow greater print speeds. See Binary and Greyscale.