When I bought my caravan, it came with a pair of Milenco towing mirrors.
Unfortunately going down a heavily rutted track, one fell off and cracked the mirror. I didn't want to spend $200 on another set of mirrors so I bought a cheap pair, they were useless, vibrated so much you can't see. I was going to buy a new pair of the Milenco mirrors, when I read an article which said you can buy replacement heads. These mirrors are excellent.