I have used this brush for years, I don’t remember when I got this brush in 2015, I got it with a Finish line cleaning kit, so far this is my favorite way of cleaning a filthy chain.
This is probably one of the best chain cleaning devices, unlike closed system witch are bit more time consuming, the Grunge Brush work as good as them but it is a simple solution, you can easily clean the cassette with the long single bristle end.
You can buy spare bristles, which I have done, which I will use when these wear out.
I don’t have any complaints yet.
Obviously recommended for cleaning filthy chain fast and easy.