I fitted these to a Royal Enfield, had to do some machining to make them accept an M8 bolt with a 1/2 inch Diameter allen head socket, rather than reaming out the diameter for the for bolt style supplied. Only expectation was that the outer diameter of these would be a little larger. An adapter supplied with the mirrors I purchased made up the difference. Would be nice if they sold a end cap finisher for this piece. Overall nice bar end adapters, the side that mounts to the handle bars is perfectly flat as its not shown in the picture.