Total
Quality

Nothing special

It functions fairly well as a mute for feedback and unwanted noise, but it really is overpriced.

For practice purposes a clean sock tied to the fretboard has better results without even spending a cent and for stage purposes... A nicer and cleaner sock surely does the same!

The only advantage it has over DIY alternatives is that it makes you look more "professional" if you show up at a gig with one on your guitar.