The Good: It's cheap, it lasts for years, and it's the quickest way to clean cassettes, chainrings, and derailleur pulleys.
The Bad: Nothing, really.
This brush is the best at what it does. It's shaped perfectly to reach into the nooks and crannies of cassettes. It's durable - I haven't worn one out yet at home. The scraping end fits in between the cogs of a cassette and is great at busting up thick, caked-on grime, and the brush gets everything sparkling clean again. What more could you want from a five-dollar tool? Whether in the shop or at home, this is my go-to tool for a dirty cassette.