The STRAIGHTLINE PERFORMANCE REV G4 850 CHASSIS BRACE is a must have item for any 850. This braces the QRS clutch tower to the down tube of the steering frame for a much needed support to that clutch tower. Made of aircraft grade aluminum for durability and stability and an easy install make it a no-brainer. Do your belts and drivetrain a favor and get one of these units. These fit all models of 850 REV G4 chassis.