I am a one man acoustic vocalist/performer. I sometimes suffer feedback issues and a friend suggested I buy one of these gadgets. So I checked them all out and decided on this.
Arrived from Thomann very well packaged. The unit looks good and fit my Taylor guitar perfectly. It is of made of plastic and has foam on the underside. It does not appear to affect the tonal quality of the guitar, at least to my ears. It does it's jobs and prevents feedback. I have tried it in a gig where I normally suffer feedback due to the stage construction being like a box and the volume I have to play at. I had no feedback issues.
All in all, a very cheap and attractive looking solution for feedback on acoustic guitars. I would recommend. Why there are not more attractive looking solutions other than black rubber available, I cannot understand. Maybe an opening for someone in the marketplace.