A backplate and wing is a type of scuba harness with an attached buoyancy compensation device (BCD) which establishes neutral buoyancy underwater and positive buoyancy on the surface. Unlike most other BCDs, the backplate and wing is a modular system, in that it consists of separable components. The core components of this system are:The backplate, a plate, usually made from stainless steel, sometimes aluminium or carbon fibre composite, which is held against the diver's back by the harness, and to which the diver's primary cylinder or cylinders are attached. A harness, which attaches the system to the diver, and may support other accessories. An inflatable buoyancy bladder known as a wing, between the backplate and the cylinder(s), used for adjusting the buoyancy of the diver when in the water. A set of cambands or cylinder bands, to hold the cylinder(s) in place.

A scuba set, originally just scuba, is any breathing apparatus that is entirely carried 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 that is required for providing breathing gas to the diver, general usage includes the harness or rigging 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. In the looser sense, scuba set has been used to refer to all the diving equipment used by the scuba diver, though this would more commonly and accurately be termed scuba equipment or scuba gear. Scuba is overwhelmingly the most common underwater breathing system used by recreational divers and is also used in professional diving when it provides advantages, usually of mobility and range, over surface-supplied diving systems and is allowed by the relevant legislation and code of practice.