211255715B Heater pipe, 60mm, rear Posted on 3 March 2018 by adminparts from chassis number 4001 (09/1950) until 1 306 307 (05/1964) the diameter of the heater pipe was 50mm. From 1 306 308 (04/1964) until the end (07/1967) the diamter of the heater pipe is 60mm.