The Hope RX4 Caliper Post Mount Standard is a drop bar compatible 4 piston calipers specially designed to work with Shimano or SRAM brake lever master cylinders, aimed for Road and Cyclocross use. Hope RX4 Caliper Post Mount Standard Features SHIMANO COMPATIBLE CALIPER RX4-SH caliper model designed to work solely with Shimano system, available in 3 version : Std Postmount Front Flat mount direct, fits directly with a Ø160mm rotor Rear Flat mount direct, fits directly with a Ø160mm rotor The RX4-SH caliper can replace the following Shimano caliper references : Flat mount : BR-R9170, BR-RS805, BR-RS405, BR-RS505 Postmount : BR-RS785, BR-R785 RX4-SH caliper will only work with mineral oil brake fluid SRAM COMPATIBLE CALIPER RX4-SR caliper model designed to work solely with SRAM system, available in 3 version : Std Postmount Front Flat mount direct, fits directly with a Ø160mm rotor Rear Flat mount direct, fits directly with a Ø160mm rotor The RX4-SR caliper can replace the following SRAM calipers : Force, Red and Rival RX4-SR caliper will only work with DOT4 or 5.1 brake fluid