This steel safety wire can save you a lot of trouble and money. The mirrors on your bike are not bolted on but instead, they are attached with a quick release connection allowing them to fall off in the event of an impact. Although originally designed for safety reasons, sometimes even a small amount of force will cause the expensive mirrors to disconnect and fall onto the road. The sight of a bus or truck behind you running over your mirror is not a pretty one and can be avoided by fitting these wires. The mirror may still pop off but at least it won't hit the ground and get smashed. The steel wires are designed to withstand a load of 17 kg, and this should ensure that the mirrors stay with the bike under normal circumstances. Very easy to install: Just "pop" your mirrors off, attach the looped end to the mirror and the other end to a fastener on the bike. Reinstall the mirrors and you're done.
Sold as a set of two.