Measuring and applying rheological material functions which are relevant to polymer fabrication and processing is something everyone should have in mind. We will address the four general categories of requirements for manufacturing the thousands of products produced from plastics. These are Profits. Appearance, Dimensional Stability and Properties. Two thermoplastic melts will be presented, LDPE and LLDPE. For the composites we will present the rheology of heterogeneous polymer melts, namely ABS and fiber reinforced ABS. Here we will show how data from a stress controlled rheometer and a capillary rheometer increase our understanding of the structure-processing-property relationships of these widely used plastics.