The GRX gravel groupset has some innovative features, as well as some that represent a forward looking approach, with inspiration from the past. If you raced cyclocross in the pre-disc brake era, you likely either had or considered a handlebar top mounted in-line brake lever or levers for your cantilever brakes. These levers allowed you to brake from the top of the bar, which was crucial when either sitting up to catch some air, or when lifting the front wheel over rough, straight terrain helped keep you tracking straight and limiting front wheel weight while transferring that weight the rear. Being able to brake without changing hand positions can be crucial to stability and control over rough surfaces.

Shimano's GRX adds a new twist, in that the BL-RX812 Hydraulic Sub Brake Levers are hydraulic. The in-line sub brake levers bring greater rider control for mixed terrain riding thanks to Shimano's category-leading hydraulic disc brakes. The lever option offers reliable and accessible braking in more positions and allows for quick access while riding upright on the tops of the handlebar. This can be a true asset with the wider bars common in gravel use. Hand transitions take longer and can disrupt the concentration and stability you rely on for safety on gravel roads.

The 82 gram Sub Brake Levers are sold individually, as Right or Left. The hydraulic fitting is straight for a clean connection. GRX's Minneral Oil hydraulic disc brake systems use the SM-BH90-JK-SSR hydraulic hose system, and that is the only version compatible with the BL-RX812 levers. Shimano developed a clean, thin new band design that sits nearly flush with bar, making the lever set-up feel natural, no bulk or protrusions. The aluminum lever and body are anodized in Black, with a subtle GRX logo, unlike the GRX gray scheme that is used on other components. The sub levers do feature reach adjust, via Hex wrench.