Specially designed brushes for cleaning hard to reach areas on most bicycles.This dual-sided brush is specifically designed for cleaning hard-to-reach areas of the bicycle drivetrain. The long, stiff bristles of the GSC-3 are narrow enough to reach between the gears of tightly-spaced modern cassettes, while the slim contoured end is capable of picking grit and grime out of tight spaces such as derailleur pulley wheels. Park Tool Brushes and Cleaning Tools Cleaning Tool UPC: 763477003539