1.Brake retarder R series is for small and mid-buses 2.Save ... No friction, much safer for passengers trip Keao brake retarder --R series electromagnetic retarders are widely used for small and ... middle bus( 7~10m)..R series Retarder is light weight, easy to install, and on ... ..For more information, please contact us now. R series retarder--KEAO Brake Retarder --China top quality