I truly love this little sticker !
At the contrary of regular tape which eventually slide/move on the fingerboard, this sticker doesn't move over time (and can be removed easilly but leave some marks of glue which can be cleaned with a tiny bit of water and soap)
I never had a classical music education, but had a cool violin at home, when I decided to learn how to play, this stickers tremendously helped me to improve both my accuracy and my confidence while playing.
It's an excellent teaching aid when you don't have a teacher available regularly to correct you !
My only regret is that the vinyl used is too glossy to my taste.
At first the light reflexions on the fingerboard really disturbed me and I was constantly turning on myself to find the best spot to avoid window/aquarium/light bulb reflecting on my fingerboard.
I reached the manufacturer (super friendly !) via email to enquiry about a non-glossy version, and it seems that unfortunatly this doesn't exist yet.
If you start learning the violin, stick one of those on your fingerboard, you won't regret it !