Motorbike manufacturers design, develop and produce motorcycles and related two-wheeled motor vehicles. Their work may include engineering frames, engines or electric drive systems, suspension, braking and electrical equipment, as well as integrating components made by specialist suppliers. Production can range from building complete bikes on an assembly line to making smaller runs of specialist or hand-built models. Products may include road bikes, touring and commuter motorcycles, off-road and competition bikes, scooters, electric motorcycles and custom-built machines. Manufacturers may also offer model development, prototype construction, testing, assembly and quality checks. Some make components or accessories alongside finished vehicles, while others focus on particular types of motorbike or stages of production.