It is shown how a very small modification to structured packing can result in a large increase in capacity. Various modifications are described, all of which cause a reduced resistance for vapour as it enters the base of each brick. In the experiments reported, a capacity increase of 30% was achieved for air-water and 15% for cryogenic distillation. The results of this investigation have been used as the basis for commercialization of a new generation of structured packings for distillation having increased capacity.