Very disappointed I was also of the weather resistance. After a few minutes the rain water had penetrated on the handlebars facing bottom side and the lamp was put out of action. The button batteries I was able to dispose of me (because it had to go fast) in the store, buy for 5 euros new.
No bargain.
Same effect a few days with my second light.
Since I started using the lamp to tie the dog only in an emergency or to them.
Definitely no traffic compatible light.