EC officials were accompanied by their counterparts from the relevant national competition authorities. The EC alluded to the fact that these companies may have violated EU antitrust rules which prohibit cartel behaviour.
Exhaust systems for vehicles are composed of the "hot end" and "cold end". The components of the "hot end" include in particular the exhaust manifold, catalytic converter, converters, as well as (in case of vehicles with Diesel engine) Diesel Oxidation Catalyst (DOC) and Diesel Particulate Filter (DPF). The "cold end" comprises in particular the mufflers and tubes.