A timing belt, or cam belt (informal usage), is a part of an internal combustion engine that controls the timing of the engine's valves. Some engines, such as the flat-4 Volkswagen air-cooled engine, and the straight-6 Toyota F engine use timing gears. Timing belts replaced the older style timing chains that were common until the 1970s and 1980s (although in the last decade there has been reemergence of chain use for many carmakers). Some manufacturers, such as BMW, are known for utilizing timing chains, because of their durability. The term "timing belt" is sometimes used for the more general case of any flat belt with integral teeth, although such usage is a misnomer since there is no timing or synchronization involved.