By interchanging the Fusion headset's 12.5mm and zero-stack lower adapters, the head tube angle can be varied by +/-0.5º.

• The table below shows the effect of different combinations of lower-adaptor and fork-travel on head tube angle, for the Xenon-E frame.
  • Use the 12.5mm adapter to slacken the head angle
  • Use the zero-stack adapter to steepen the head angle