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The view into one of the fuel feed passages showing two of the "steps" where the diameter of the passage decreases.

Note the hypergol feed line. This line delivers pyrophoric fluid (fluid which spontaneously combusts upon contact with oxygen) into the thrust chamber through igniter fuel orifices in the injector.

This particular feed line leads to an igniter orifice between the inner and outer circular baffles.

Picture 2 of 2.

This photo is exposed for the interior of the fuel feed passage.

Also note the holes in the aft (top) side of the passage, where fuel is delivered to the 14 rows of fuel ring grooves.