Sram ex1 8 speed rear mechsrams ex1 8 speed rear mech is a world first as its the first rear mech thats specifically designed for e mtbs it adopts shift technologies from srams top of the line xx1 and x01 models for the ultimate in quick and accurate shifting and reliable chain retention its also been specifically engineered to cope with the extra torque that is generated as you shift through your e mtbs power assisted drivetrain features materialaluminium cage speed8 speed compat