Harley Benton Feedback Buster 88mm

Pros:
Cheap
Kills feedback
Reduces sound by about 30%

Cons:
Some cosmetic issues due to manufacturing process when seen up close

It looks ok and does the job. Was too small for my Baby Taylor BT1(e)

Used this with my LAG acoustic guitar and fits perfectly, killing feedback as it was supposed to do.

It does not fit the smaller sound hole of Harley Benton Kahuna CLU-Bass but you can carefully shave off from around the mute using a craft knife to fit it, without cutting the top lip so it won't fall off. With this, I no longer have feedback issues in high volume environments. Acoustic volume is less as expected, but the output sounds a bit more focused with this installed, which I find is a positive for most acoustic instruments.

Does not fit Paco Castillo classical guitar

Used as base for mounting Fishman active pickups to soundhole. And that worked. Cannot say anything about normal functionality

I purchased this for a Tanglewood TW2 TSE travel guitar and unfortunately it was a little bit too small. I added some electrical tape to increase the circumference of the soundhole cover and it now fits perfectly.

The cover itself is decently made and seems durable.

This is the second feedback buster I bought, as the first one I bought was too big.
Well, this one was too small, but through no fault of Thomann. It ends up the hole on my acoustic electric bass is an odd size.

The item itself is well made. The rubber is of good quality, and should last for many years.

My nylon-string guitar has a slightly larger diameter sound hole than what is "standard" (??). I tried a $14 (USD) one that was even looser fit, falling into the guitar loose! Anyway, this one for considerably less money and same quality (and with a few little bits of clear medical tape to secure it) does the job fine!

So note the dimensions and see what happens!
But if it fits it will do what it's supposed to!

Perfect for cutting feedback. Used it with a Yamaha guitar.

this feedback killer is only 85mm diameter & not 88mm like indicated. Unusable!!!