Pack of 1 piece OEM design factory direct replacement HID Ballast control module unit; the replacement ballast is not OEM but is fully Plug-and-Play and will be direct replacement of your factory unit. Compatible Replacement for Mercedes E Class W211 S211 2003-2009 OEM Number: 5DC00906000, 5DC00906010, A2118705585, A2118705685, A2114420203 Please verify your factory ballast and connectors matches the product on the image exactly before placing an order. Certain manufacturers may change the ballast type when there is a mid-cycle refresh or new production date. Please note that the most common reason for failure is water in the headlight. If you headlight has water in and your ballast has failed because of it, you may need a new headlight as a replacment ballast will fail again.