such dies would require modification with suitable passages to transfer and discharge quench air received from distribution passages 44 also in accordance with the invention heating elements 74 76 are respectively contained in passages 80 82 between plates 16 b 16 c and 18 b 18 c each passage is again preferably formed by respective pairs of aligned and abutting recesses 84 86 and 88 90 in plates 16 b 16 c and 18 b 18 c these heating elements 74 76 which are preferably electrically operated heating elements may be advantageously situated between the respective air and liquid passages 27 54 and 29 56 so as to heat both the liquid and the air traveling to extrusion die 14 sufficient heat may also be supplied to heat the extrusion die 14 itself to the appropriate operating temperature fig4 and 5 illustrate another apparatus 10 u2032 constructed in accordance with the invention in this embodiment apparatus 10 u2032 again comprises a multiple plate assembly or manifold structure 12 u2032 coupled with an extrusion die 14 u2032 manifold structure 12 u2032 and die 14 u2032 are similar to the first embodiment except that a five plate construction is used instead of a seven plate construction thereby eliminating.