This is a Genuine BMW Channel Seal Outer Door Rear Left, part number 51357176777. It is used to seal the outer edge of the rear left door on a BMW vehicle. This product is made by BMW and is an authentic replacement part for your vehicle. It is important for maintaining the integrity of the door and preventing water or debris from entering the interior. This channel seal is specifically designed for the rear left door and is made to fit perfectly on your BMW.