On a daisy-wheel printer the complete set of characters is held on a removable wheel which consists of a central collar radiating out from which are a set of spokes, each ending in a single character. The wheel spins round to align the required character with a single hammer. The hammer and wheel assembly move across the paper striking it through an inked ribbon. These printers can produce high quality output but are limited to the range of characters on the wheel. Changing wheels is simple, this provides alternative fonts, but is no substitute if a wide range of fonts is required. They are quiet noisy and are used for low volume office work. They are obsolete now.