Coloration on the machine is nowadays an essential precondition of flexible, economic working in the plastics processing industry. Automatic metering and blending units are used as individual devices, but also to an increasing extent as an important component of central material supply systems. Instead of the hopper being mounted directly on the feed opening of the processing machine, it is becoming a fixed element of injection and blow moulding machines and of extrusion lines. For figures and literature see German text on pages from 1097 to 1099.