If you clean the suction cup and the surface with alcohol, it will not come off. The edges of the plastic hit the glass and make a noise.

The suction did not work at first but then I did the trick where you add a drop of water to remove excess air and it has been stuck for 1 year without falling off or deteriorating.

It could be a bit bigger in size.. But my main issue is that the suction cup that holds it doesn't stick for long... I've had it come off twice during a walk..
Update: Two months later, it sticks again now that it's worn out.

The first one didn't stick to the glass at all, and the second one fell off after 15 days. I wouldn't choose it again.

Strong suction cup, therefore good application. Good size that is discreet and phosphorescent when reflecting lights