Park Tool CB-4 is a 100% biodegradable, natural, plant-based degreaser formulated for use in the CM-5.3 Cyclone Chain Scrubber, CM-25 Professional Chain Scrubber, or with a scrubbing brush as a general purpose degreaser. When used with a chain cleaner, CB-4 gets bicycle chains clean inside and out so they're good as new. Will not harm alloy, plastic, rubber, or carbon fiber parts, so it's safe to use for cleaning cassettes, chainrings, pulleys, or any other component that accumulates muck and grime.