Park Tool GSC-4 Cassette Cleaning Brush -Having a clean drivetrain allows for smoother shifting and makes for a more efficient bike. The Park Tool GSC-4 Cassette Cleaning Brush should be a required tool for every rider's home tool quiver and is a simple but important tool in keeping your bike working at its best. The brush is basically an oversized toothbrush with reinforced nylon bristles. This Cassette Cleaning Brush is great for getting all the dirt that gets trapped on your cassette or freewheel. FeaturesStiff nylon bristles Concave bristle shape Hole in the handle so you can hang it on your tool rack | Park Tool | GSC-4 Cassette Cleaning Brush Blue