A scuba set is any breathing set that is carried entirely by an underwater diver and provides the diver with breathing gas at the ambient pressure. (Scuba is an anacronym for self-contained underwater breathing apparatus.) Although strictly speaking the scuba set is only the diving equipment which is required for providing breathing gas to the diver, general usage includes the harness by which it is carried, and those accessories which are integral parts of the harness and breathing apparatus assembly, such as a jacket or wing style buoyancy compensator and instruments mounted in a combined housing with the pressure gauge, and in the looser sense it is used to refer to any diving equipment used by the scuba diver, though this would more commonly be termed scuba equipment. Scuba is overwhelmingly the most common underwater breathing equipment used by recreational divers. A scuba set is also used in professional diving when it provides advantages, usually of mobility and range, over surface supplied systems.