THE MATERIAL WORLD / only pounds 634,500, car included

This is the most sought-after wing mirror in the world. It is made by Citroen, and is available from Citroen dealers for pounds 72.55. They cannot sell you a car to go with it, because the model for which it was made, the CX, went out of producti on in 1989. But you can buy a car with these wing mirrors: they are fitted to the McLaren F1 supercar, which costs pounds 634,500. If you want something cheaper, you'll find them on the Jaguar XJ220, the Aston Martin Vantage, the Lotus Esprit, the AC Ace , and the TVR Griffith and Chimaera.

What does everyone see in this mirror? It looks good, and it's cheap. International legislation makes an item like this surprisingly expensive to engineer, so makers of low-volume cars prefer to hunt around the parts warehouses of the big manufacturers and buy their bits instead. To giveyou an idea of how expensive minor parts can be: tooling up to manufacture the rear lights of the Aston Martin Vantage - simple, circular things - cost the firm pounds 100,000. Aston wanted to use Chevrolet Corvette lamps for the Vantage, but Chevroletwoul dn't let them, perhaps because Aston is owned by its arch rival, Ford.

Some cars are greater than their parts Next to the steering wheel of a brand-new, pounds 175,000 Lamborghini Diablo SE is a Morris Marina indicator stalk. And this is not the only thing the 200mph coupe shares with the sad old Morris: there's the windscreen-wiper stalk, too. Such plagiarism i s not new to Lamborghini, which robbed the Austin Maxi of its indicator stalk for its Miura model in 1966. The Morris Marina exterior door handle also used to be a very popular item: it appeared on the early Lotus Esprit and the Triumph TR7, and canstil l be found on the Range Rover four-door and the Land Rover Discovery.

The Citroen Marina with a Lotus badge Lotus makes most of its Esprit model, but not the wing mirrors, tail lights (from the Rover SD1), door handles inside (Vauxhall Cavalier on late models, Morris 1100 on early ones) and out (Vauxhall Cavalier on late models, Morris Marina on early ones), c ontrol stalks (Morris Marina) and rear lamps (Toyota Celica). For all these items, as well as mechanical components, it's cheaper to buy off the shelf. Some parts, like the Citroen CX wing mirror, pop up everywhere. Aston Martin's DB7 has some more obscure items, including rear lamps come from the Mazda 323 Model F and switches from the Jaguar XJ6 and Ford Scorpio. TVR uses Fiesta tail lights for its Ch imaera, and Cavalier rear lamps - fitted upside down - for the Griffith.

Nice air vent, shame about the car Years ago, Austin hijacked the Jaguar XJ6 air vents for a facelift of its misbegotten Allegro. So desperate were the copy writers to find something positive to say about the Allegro that they alluded to this tenuous Jaguar connection in advertisements fo r the car.