Abstract: A transition device for a combine harvester includes a body having an inlet end and an outlet end. A plurality of vanes are positioned on an interior facing surface of the body for guiding crop material through the transition device. Each vane has a first end positioned either on or adjacent the inlet end of the body and a second end positioned either on or adjacent the outlet end of the body. An arc length between the first ends of two adjacent vanes of the plurality of vanes is less than or equal to an arc length between the second ends of the two adjacent vanes of the plurality of vanes, such that the crop material can expand between the two adjacent vanes upon travelling along a trajectory from the inlet end to the outlet end of the transition device.