Flange, also known as a flange disc or boss, is a component used for connecting pipes to each other or between equipment, such as a reducer flange. A flange connection or flange joint refers to a removable connection formed by the combination of a flange, gasket, and bolt. Pipe flanges are flanges used in piping systems, while equipment flanges refer to the inlets and outlets of the equipment. Flanges have holes, and bolts secure the two flanges together. They are sealed with a gasket. Flanges are available in threaded (screwed) connections, welding flanges, and clamping flanges. Flanges are used in pairs; low-pressure pipelines can use threaded flanges, while those above four kilograms of pressure require welding flanges.