Just bought 2 of these.....one for my wife......before a week of cycling in Brittany. I can only say that they were brilliant. They fit in seconds, and stay rock solid. I have straight handlebars, with bar extensions added. They clip onto the extensions (left or right) and can be adjusted to give an excellent view behind. If you haven't got bar extension, it's worth picking some up just to put these mirrors on!. Very highly recommended.