Abstract: A built-in packing for the material exchange and/or heat exchange between gases and liquids is composed of a plurality of undulating lattice-like elements arranged next to each other and each mounting element has channels formed by the undulations extending at an angle relative to the vertical direction and extending parallel to each other, wherein the channels of always two adjacent mounting elements intersect each other. Continuous longitudinal struts are provided at the bottom of the channels, wherein the longitudinal struts have contact plates at the ends thereof, and wherein the contact plates are components of an upper and a lower horizontal closed edge strip. The longitudinal struts are connected through transverse struts in a framework-like manner, wherein the transverse struts extend in horizontal planes which extend parallel to the two edge strips.