Car part manufacturers produce components and assemblies used in cars, supplying vehicle makers, repair markets and parts distributors. Products may include engine and transmission components, braking and steering parts, suspension systems, electrical and electronic equipment, body panels, interior fittings, seats, glass, seals and fasteners. Some businesses specialise in a single component or material, while others make a range of parts or assemble larger systems. Work can involve interpreting technical specifications, designing or adapting components, machining, casting, moulding, pressing, welding, coating and assembling. Manufacturers may use metals, plastics, rubber, composites and electronic materials, with production methods suited to the part and the volumes required. Inspection and testing help check dimensions, durability, safety and performance against customer or vehicle-industry requirements.