NBR (nitrile butadiene rubber). BMW 5 Series Petrol Saloon RWD -- E39 523i 1995|1996|1997|1998|1999|2000 2494cc 125KW 170HP M52 B25 (256S3);M52 B25 (256S4). BMW 5 Series Petrol Saloon RWD -- E39 528i 1995|1996|1997|1998|1999|2000 2793cc 142KW 193HP M52 B28 (286S1);M52 B28 (286S2).
