The 10-spd GRX ST-RX400 Dual Control Lever with Caliper Set forms the Dual Control STI system mechanical shift/hydraulic disc brake use with GRX 10-speed The Right and Left sets are for the mechanical derailleurs and front hydraulic disc brake for the 2x drivetrain. Each side is sold as a set, with lever and pre-bled housing assembly to the Flat Mount disc caliper. 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 road 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-RX400 Dual Control Lever and front/rear appropriate 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.