Sram guide re e mtb disc brakesrams guide re e mtb disc brakes are specifically designed and optimised for use with the exiting new e mtb category they have the braking power to deal with the higher speeds more aggressive use and the added weight of your power assisted trail conquering weapon guide re brakes feature a 4 piston caliper taken from srams downhill range and use the heat resistant dot 51 brake fluid which prevents brake fade on those long descents features body materialfor