This is the low pressure return hose from the brake accumulator sphere and valve to the brake reservoir. There are two of these hoses per car on the series 1 models (before VIN 30000). From VIN...

This is the front brake pump feed hose to reservoir.  1966-1980 from VIN 5001 onward

This is the high pressure pipe from the front brake pump to the accumulator on the left hand side of the engine.  It is suitable for all cars from approx 1973 fitted with the bigger bore...