Flexible couplings are used to link two rotating shafts that are not aligned in order to transmit the rotational power, known as torque, from one shaft to the other. Most flexible couplings consist of two hubs and a middle assembly; each hub attaches to a shaft while the middle assembly flexes between the hubs to accommodate the misalignment of the two shafts. Shaft misalignments are generally either parallel or angular and cause complications to transmitting rotational power from one shaft to another in the form of stresses, loads, vibrations, and other forces, which vary from one type of misalignment to another. Flexible couplings are used in a broad range of applications, such as in motor vehicles, conveyors, escalators, agricultural, forestry and mining equipment, aeronautics, robotics and space exploration, among others.

Boston Gear manufactures gears, gear drives, bearings, valves, shaft collars, couplings, and other power and fluid transmission components. The company, founded in 1877, is headquartered in Charlotte, NC, and meets International Organization for Standardization (ISO) standard 9001:2008 standard.