Litens and INA do not show parts for the E70 X5 in their catalogs. You will find the INA OAP listed on retailers' websites, however. Litens pulley is an OAD and works sightly differently than the INA and BMW Diesel Parts OAP. I'm going to install a Fluidampr so I actually am going with the OAP now. INA is an OEM to BMW for belt drive components. BMW Diesel Parts seems decent, but I've never perosnally dealt with them. FCP Euro sells the OEM INA p/n EA0183 and Cascade German Parts has what might be the OE M57 BMW p/n 12 31 7 560 483. You need to be sure that the required spacer is included or ensure you buy one and install it. Old pulley should come off (I'm not sure all or any X5s got the OAP hence tge lack of catalog cross reference) and you might need an OAP install tool to torque the new one on. The new OAP should have a cover/protector included also.

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8/2011 X5 xDrive35d Sport, Black Sapphire Metallic, Black Nevada Leather, Fine Burr Walnut Trim
2/2001 M5, Jet Black, Exclusive Complete Black Walk Nappa Point Heritage Leather, Black Cubic Trim