They are not bad at all. When installing, the mirrors come with two rubber washers, one for each mirror. So when you tighten each side up, they get sort of nipped or act as a buffer between the bars and mirror base. I only got them because my originals gave me problems-i.e wouldn't stay tight, and to be honest, although these bar end mirrors are small they are quite
effective once set up. And to me, just my opinion, I think they suit the size of the bike.
How long they will last is anybody's guess, but for the price and a little drilling of the mirror body to take the BMW size bolts (8mm) you cant go wrong really, and they swivel out the way.