Tip:
Remove the mirror that fits to the brake master cylinder. If damaged you are looking at a lot more than $20 to replace it. You only really need one mirror on your offside (Right side in USA, left side down here. AUS.) Also for those down here, take the bar clamp for the left mirror and refit it on the right with the right mirror. Will save the master cylinder if the mirror takes a good hit.

 

Good tip! And another reason to swap out the stock mirrors.

 

I don't know about the other 49 states in the USA but in Washington state you are required to have BOTH a left and right rearview mirror. Get one of the various METAL-TYPE mirrors with the flexible stem (mine was called a Bikemaster) and you can actually see rearward AND fold them inward for off-roading.