As a speaker, it has good performance. A major advantage is that you don't need to insert the headphones into the helmet lining. It sticks on the outside and turns the entire helmet into a speaker.

On the negative side, the microphone (connected with micro USB to the charging port) does not make good contact, resulting in not being able to hear you and having to shake the connection to see if it will work again (at the moment, of course, when you have an ongoing call and possibly driving).
Also, after a week, the adhesive started to come off. However, the packaging does include a spare adhesive.
In my opinion, it is not worth 45 euros. If it was under 30, it would be worth trying.
It replaced a 10 euro Bluetooth that worked perfectly for 4 years, and the only reason for the change was to avoid opening the lining in the new helmet to insert the headphones.

After a few weeks of use, the microphone came off and got lost, and no replacement was found, rendering the Bluetooth useless.

The solution was found. After much searching, I found the manufacturer in China (http://www.alex-technology.com/). They sent me a new microphone for 8.5 USD. The package included 2 microphones, one to be inserted internally and one externally (like the original). I used the internal one, the connection is better than the original, and I believe it won't come off.

Now that the solution has been found, I think it deserves 4 stars.