This is truly a quality tool I've needed for many years. This brush & gear teeth are perfect for cleaning my rear cassette, derailer & idler wheels. Beats heck out of the toothbrush & Q-tips I've used till I got this tool. It doesn't leave fuzzy cotton between gears like the Q-tips did.
This isn't fancy, but it sure is designed well for its purpose. I can get in between the cogs with either the brush or the plastic toothy end of the tool, helping to keep my drivetrain clean. It is durable. The bristles are pretty stiff, so don't worry about fraying them with aggressive scrubbing. A well-placed hole allows me to hang it from my peg board in the shop area of my garage.
I like this because it allows me to do a very thorough cleaning of bicycle cogs. Even with regular chain cleaning, winter riding can gunk up the cogs and rear derailleurs, so this tool is great for getting to the hard-to-reach places.
Bristles are stiff and long enough to get out caked on grease on both cassette and between the small and large chain rings.
Not sure if the toothed semi-circle thingy is all that useful.