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Detail of the No. 2 LOX (back) and fuel high-pressure ducts (the No. 1 side of the engine is located 180° around the engine and has similar, but longer high-pressure ducts).

These ducts carry high-pressure propellants from the turbopumps to the main propellant valves, on their way to LOX dome and the fuel manifold, respectively.

As an early production engine, the high-pressure ducts are flexible, internally-tied high-pressure ducts. The ducts had flexible bellows to allow for relative movement between the turbopump and main propellant valves. Later production engines had rigid high pressure ducts.

In this photo, one of the flexible bellows is visible on the turbopump (bottom) side of the fuel high-pressure duct. Note the silver bands or caps (which were apparently installed to protect the bellows) on either end of the straight portion of the high-pressure ducts on these early engines. The lower cap on on the fuel high-pressure duct is missing, allowing a view of the bellows.