External rear view mirror with air guidance

The housing (1) has a housing part (5) comprising walls (8) that surround an opening (3), where the opening is formed for a mirror glass on a rear side (2). Another housing part (4) and the walls of the former housing part comprise opposite inner sides (10, 11) that are turned toward each other, where ribs (12-14) are arranged at the inner sides and run parallel to the rear side. The ribs extend from one of the inner sides to the other inner side up to a gap (15) in a direction of mirror height. The ribs form an intermediate space for retaining a labyrinth seal.