A swathing unit (12) for an agricultural mower (4) includes at least one side deflector plate (14) that defines one side of a discharge opening (18) and is adjustable between a wide swath configuration and a narrow swath configuration. The side deflector plate (14) is attached to a pivot mechanism (30) and is angularly adjustable about a pivot axis (X) between an inner position and an outer position. The side deflector plate (14) comprises a first plate element (20) that is attached to the pivot mechanism and a second plate element (22) that is attached to the first plate element and is adjustable to adjust the overall length of the side deflector plate. The second plate element is attached to a control element (32) that cooperates with a guide element (42) to control adjustment of the length and the angular position of the side deflector plate. Movement of the control element relative to the guide element causes simultaneous adjustment of the length and the angular position of the side deflector plate (14).
