The packing includes a pile of plates having corrugations forming a succession of channels comprising fins, each fin being made up of at least one band cut out in one of the plates and remaining secured to the plate on at least one side, the band being deformed so as to create an orifice forming a discontinuity on the surface of the plate, wherein the direction of the channels of a plate forms a non-zero angle with respect to the direction of the edges of an adjacent plate. Finally, the lengths of the fins of a channel are different from those of the fins of a neighboring channel.