A Melt Flow Index tester measures the melt flow rate (MFR) or melt mass-flow rate (MFR) of a polymer. This is a significant quantity in the plastics business since it reflects a polymer's flow properties when melted under certain conditions.

Melt flow index testing is important for quality control and process optimization in industries where polymers are used, such as in the manufacturing of plastic products, films, fibers, and more. It enables producers to ensure that the polymer materials they use have the necessary flow properties for their intended application.