| The existing wing mirror back does not come apart along the seams where the chrome caps fit, so I would suggest they are a thin cap that is glued ontop in some manner.
 They're not to my taste so have never really investigated them. I had my Range Rover Sport Supercharged's wing mirros colour coded and I think this looks much nicer than the chrome IMHO.
 
 Here's what they looked like, not just the top part like the caps.
 
 
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  Discovery 4 HSE     |  |     | Click image to enlarge |  1998 110 TUM HS FFR Hard Top XD WOLF
 1982 Series 3 Hard Top
 1998 90 TUL FFR Hard Top XD Wolf
 1993 90 Tdi
 
 *Gone: L405 4.4 VSE, L462 D5 HSE LUX,  L663 Defender 110 HSE, Discovery 3 HSE, 2014MY Range Rover Sport 5.0 Supercharged AB Dynamic;  L405 Exec Vogue SE 4.4,  5.0 Supercharged Autobiography, Defender TDCi XS CSW, Defender TD5 HT, Vogue SE TDV8, Vogue TD6, RRSport SC 4.2V8, Classic 3.9 Vogue Auto,  Land Rover Series 3 SWB
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