Traditional ZS44/EC44 headset in 44mm head-tube
Many GeoShift headsets use an EC44 upper bearing cup. That is, the upper bearing cup sits outside of the head-tube, and is pressed into a 44mm inner diameter tube. These are used in applications where a traditional (non-angle adjusting) headset would typically use a ZS44 upper bearing cup. The reason for this is purely spatial - by moving the bearing outside of the head-tube, more angular movement of the steerer-tube can be achieved. In fact, a 2-degree angle change in a 44mm head-tube with a 1 1/2"-1 1/4" tapered steerer-tube is only possible with an EC upper bearing cup.