When installing a movable mirror, use a fixed indicator tube from the ET3, or attach the mirror with a metal rod with a screw end through the underside of the handlebar. This prevents the mirror from turning when you shift.
Good to know: Mirror legislation
Older vehicles that do not possess an EU registration, require a minimum reflection area of 60cm² (just over 9in.²) on each of their mirrors. An European approval emblem is not absolutely necessary. Current scooter models are all registred according to EU legislation. The mirrors that are attached to them must have EU approval markings.
Mirrors that have less than a 60cm² reflection area or no EU approval markings are not meant for (leagal) road use.
The minimum number of mirrors required depends on the first day of registration
* "registered according to EU legislation" are vehicles since 01.10.2005. Check your registration certificate for the EU entry (digit K).