BorgWarner BERU Systems GmbH (commonly known as BERU) is one of the world's leading producer of diesel glow plugs. A glow plug is a heating element that preheats the air in a diesel engine's cylinders in order to facilitate starting. BERU's other cold-start diesel technologies include flame starting and instant starting systems. Other products include automotive lighting, heaters, ignition coils, spark plugs, and tire safety systems. BERU also offers products for the automotive and truck aftermarket. In 2009 US automotive powertrain manufacturer BorgWarner bought out its remaining stake in the former BERU AG, sparking the plug maker to change its name.