The Melt Flow Indexer is a dead-weight extrusion plastometer. It consists of a thermostatically controlled melting chamber (the barrel) in which the polymer under test is heated and from which it is extruded through a standard die under standard conditions of load, which is, of course, made up of the combined weights of the extrusion piston and the loose weight both of which are carefully calibrated to well within the most stringent limits.