Another possibility.

What are the other items above and below this in the list? They might help!!

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Note added at 47 mins (2006-12-02 11:36:15 GMT)
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Some examples: for use with caravans

WIND DEFLECTORS

A wind deflector on a car can possible arouse more discussion than any other caravanning accessory. It is difficult to find someone who has tried a deflector to state other than that it is beneficial. Yet the simple truth is that some deflectors do more harm than good.

It should be remembered that anything which is attached to the roof of a vehicle, whether a pack rack or wind deflector, increases the fuel consumption. If, for example, a wind deflector increases the wind resistance created by a car by 10% then the corresponding resistance on the caravan must be reduced by at least 10% before any advantages can be expected.

http://www.caravanandcampingsa.com.au/page.asp?parentid=22&p...


Also:

http://www.dw-tuning.co.uk/automotive-equipment/roof-wind-de...

for lots of pretty pictures of "wind deflectors" for different makes of vehicles