This REP case saver is a money saver in the event of a chain derailment. If the chain wraps up around the front sprocket on a CRFX it usually smashes a hole on the crankcase costing over 600 to repair. REP case savers stop the chain from wrapping up by using the upper chain roller as a brace for the case saver. Prevention is better than the cure for only 15.99!!