A baffle (50, fig 5) for mounting to an inner wall of an exhaust tube comprises a tube engagement surface 52 and an exhaust engagement surface 54A. The tube engagement surface comprises a convex surface of a constant first radius of curvature about a first axis. The exhaust engagement surface is adjacent the tube engagement surface and comprises a concave surface of a second radius of curvature (r5, fig 6) about a second axis generally perpendicular to the first axis. The baffle disrupts a boundary layer of exhaust gas and redirects urea injected into the exhaust gas away from the inner wall. There may be a second concave exhaust engagement surface 54B facing a direction opposite the first exhaust engagement surface. The baffle may have a T-shaped cross-section. A height of the baffle (H1, fig 6) may be between 10% and 50% of the radius of the exhaust tube.
