text: "Upper bainite" forms around 400–550 °C in sheaves.  These sheaves contain several laths of ferrite that are approximately parallel to each other and which exhibit a Kurdjumov-Sachs relationship with the surrounding austenite, though this relationship degrades as the transformation temperature is lowered.  The ferrite in these sheaves has a carbon concentration below 0.03%, resulting in carbon-rich austenite around the laths.
  The amount of cementite that forms between the laths is based on the carbon content of the steel.  For a low carbon steel, typically discontinuous "stringers" or small particles of cementite will be present between laths.  For steel with a higher carbon content, the stringers become continuous along the length of the adjacent laths.