Band heater – one larger than others in extruder!

why is one of the band heaters larger than others in the equipment list for the extruder? injection machine its all 35x45mm, and the extruder says 3 are 35x45mm and 1 is 40x45mm WHY? the metal tubes are all the same size. Im about to order some parts online but cant understand the one larger component. if someone can allow me to understand this…



The larger one is for the nozzle, look at the construction video.