The packing is the most important component of the system. The packing provides sufficient area for intimate contact between phases. The efficiency of the packing with respect to both HTU and flow capacity determines to a significance extent the overall size of the tower. The economics of the installation is therefore tied up with packing choice. The packings are divided into those types which are dumped at random into the tower and these which must be stacked by hand. Dumped packing consists of unit 1/4 lo 2 inches in major dimension and is used roost in the smaller columns. The units in stacked packing are 2 to about 8 inches in size; they are used only in the larger towers.