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The marking for No. 120 tube on the injector end ring, at approximately the 5:00 position on the injector.

Picture 2 of 2.

The marking has the actual "120" marking, spanning about 2 1/2 tubes, with an arrow pointing to the injector under the "0" digit; the up-arrow is centered on a tube.

As with the No. 60 tube, the arrow is pointing toward the injector, even though both the No. 60 and No. 120 tubes are "down" tubes. (Recall that fuel flows through the tubes comprising the thrust chamber to provide regenerative cooling; every other fuel is a "down" tube, carrying fuel from the forward end of the engine to the exit plane, where the fuel return manifold then redirects the fuel back up an adjacent "up" tube.)