Shimano GRX BR-RX410 Hydraulic Disc Brake Caliper - Rear Flat-Mount W/Fixing Bolt 25mm Mount BLKShimano GRX BR RX410 Hydraulic Disc Brake Caliper Rear Flat Mount W Fixing Bolt for 25mm Mount Black. The GRX BR RX410 disc brake caliper brings a new level of control to gravel cycling with enhanced modulation and a quicker initial braking point. And despite its compact construction the system is quieter and easier to maintain. GRX BR RX410 flat mount 2 piston brake caliper has 10% wider pad clearance to decrease brake noiseOne Way bleeding makes