The Weistec Engineering Billet Oil Filter Cap for the S63 and S63TU engines is designed as a direct replacement for the plastic OEM cap. The Billet Oil Filter Cap is installed in the exact same manner as the OEM cap, using the same O-Ring that comes supplied with new oil filters. Furthermore, a drain plug has been integrated in the design of our Oil Filter Cap which is not featured on the OEM design. The drain plug allows for less mess when changing the filter. The OEM cap would be full of oil when being removed causing oil to spill all over the cap. Simply remove the drain plug to let most of the oil drain into the pan, then remove the Weistec oil filter cap to change the filter.