The GRX ST-RX600 Dual Control Lever with Caliper Set forms the Dual Control STI system mechanical shift/hydraulic disc brake use with GRX 11-speed The Right set is for the rear derailleur and rear disc brake. It can be used for both 1x and 2x GRX drivetrains. The Left set is for the front derailleur and front disc brake when using the 2x drivetrain. Each side is sold as a set, with lever and pre-bled housing assembly to the Flat Mount disc caliper. If you are building a 1x GRX bike, a GRX BL-RX600-L Left brake-only lever is available (BR-RX400 caliper sold separately). Shift wise, you get the smooth running Optislick stainless steel shift cable and OT-SP41 pre-lubed housing. The Right set also includes the required, more flexible OT-RS900 loop that must be used with the rear derailleur for proper rear shift action.

Shimano developed GRX components for the rough terrain and mixed surfaces that make gravel riding so challenging, fatiguing and fun. The shift/brake lever ergonomics make for easier leverage, hand positions, comfort and tactile use despite the constant vibration and small impacts of gravel riding. The lever blades feel correct and proper with a standard road drop bar shape, as well as the flared drop bars popular for gravel. Admittedly, they appear larger than Ultegra R8020 levers, but the increased size and variable shape of the levers definitely afford a real advantage on rough terrain, and deliver light, yet precise and positive shift action.

The set detail consists of the left-side ST-RX600 Dual Control Lever and front/rear appropriate BR-BR-RX400 Flat Mount hydraulic disc brake caliper with IceTech finned disc pads, and all necessary hardware. The system is pre-bled and connected with the SM-BH90-JK-SSR hydraulic hose system from lever to caliper. Shimano's Mineral Oil hydraulic system makes it fairly simple to set the proper housing length and bleed for best braking contact.