In the past in the United States Caterhams were sold as kits only, lacking some modern safety features required of manufacturers, but which are not required for individually assembled vehicles. Buyers could either choose to construct the cars themselves or pay their regional dealers or local builders to assemble them. Typically the engine and transmission are sourced separately as a unit – often from Caterham – but all other components (including frame, suspension, differential, driveshaft, interior, wiring and instruments) were provided in kit form.