Abstract: An extrusion process and apparatus is described for the manufacture of a thermoplastic resin-filler composite product having a desired resin-filler mixture comprised of 60-20% by weight of a thermoplastic resin and 40-80% by weight of a filler. A resin-filler mixture, in homogeneous form, is extruded through a die at a temperature above the softening point of the resin to form an extrudate having a desired cross-sectional shape. The extrudate is then passed through a die land at a temperature of above the softening point. From the die land the extrudate is cooled in a cooled shaper and transferred thereto through a thermal barrier insert member which is disposed in contact between the die land and the cooled shaper whereby radial pressure to counteract radial expansion tendencies of the extrudate is maintained during the passage. The cooled shaper cools the extrudate to a temperature of about at least 20° C. below the softening point of the resin.