Fluorescent lamp tubes are typically straight and range in length from about 100millimeters
(3.9in) for miniature lamps, to 2.43meters (8.0ft) for high-output lamps. Some lamps have the tube bent into a circle, used for table lamps or other places where a more compact light source is desired. Larger U-shaped lamps are used to provide the same amount of light in a more compact area, and are used for special architectural purposes. Compact fluorescent lamps have several small-diameter tubes joined in a bundle of two, three, or four, or a small diameter tube coiled into a spiral, to provide a high amount of light output in little volume.