no answer here...
for 40$ and free worldwide shipping, i decided to give them a try.
i had no further experience with other DB piezo pickup, except for the Palatino EUB that i have, and have piezo but no acoustics..
so, i found them very nice. very easy to install. no need for pro job.
its fits well my low budget and my cheap old 63 KAY C1.
i didn't gigged with it yet. but tried to record it into my humble home studio and its sound nice. with shure sm57 below the the bridge and mixing together the two sources, i can get nice sound.
but take my words with a grain of salt...
i am only a starter on the double bass.
but for only 40$ and free shipping - its not big risk to try, in comparison to the much expensive alternatives out there.