The tail lamp read easily as an alternative to existing lamp mount. If you look not very accurate, you do not see that there is a battery light. The luminosity is normal not to taillights. The large reflector, as with standard taillights, increases visibility.
It is very pleasant that it has a normal pressure switch on / off, and no 20 flashing modes that you have to click through Ausschallten all.
Rainy weather has the lamp so far coped well without complaint.
For me, clearly the best lighting solution, price and the handling.
Note: The light is of course not StVO approved.