Je n''ai pas compris grand chose aux photos et la vidéo ne me semble pas assez explicite sur l'installation...
Le trou de vissage sous la lampe sert à resserrer l'élastique pour maintenir la lampe (qui est légèrement orientable par rapport à son support).
La "pièce" sert à faciliter le positionnement de l'aimant par rapport à la lampe.
A noter que dans mon cas, la lampe se trouve entre la roue et le support du porte-bagages, donc elle ne gêne pas du tout l'installation de mon sac, et elle est "protégée" dans le local à vélos...

Relatively simple to mount - ~I had trouble with the rear light, but Randi from Reelight sent me a replacement very quickly. All now working and the fact that I don't need to worry about batteries and the lights continue to flash for a time after stopping gives me comfort. An excellent product

Bought them from another dealer, but impossible to attach:
one of the magnets couldn’t be tightened, kept going loose.
The lights themselves couldn’t stay tight, could just wriggle them loose with no effort. And yes I really tightened with full force.
Also the dealer have send me the standard CIO though they sold
It as the + version, and it had clearly been opened before.
I’ll give you guys the benefit of doubt since so many people have left positive reviews, but I’m really disappointed.

The lights work well and last a decent time after stopping. However they are more noisy than expected, even when the distance to the magnet is a bit larger than indicated by the instructions. When installing the lights, you should be careful not to tighten them too much. I might have ruined the screwhead on one of the lights during installation, as I wasn't sure how tight it needed to be, to stay in place in the long term.

Un excellent feu de vélo qui s'allume automatiquement dès qu'on commence à rouler
Fonctionne parfaitement, très efficace
Marche avec toutes tailles de fourches
Je recommande vivement!!