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.

GeoShift 2-Degree EC44/EC44 headset installed in same 44mm head-tube

The only drawback to using an EC upper bearing cup instead of a ZS bearing cup is added stack height. GeoShift EC44 upper bearing cups have 10mm more stack height than a comparable ZS44 cup. If you currently have your stem slammed on the headset (no steerer-tube spacers used) with a ZS44 upper cup, it'sa good bet that your fork's steerer-tube will be too short to accommodate the GeoShift headset . If you have at least 10mm of spacers, which is most often the case, you will simply need to remove 10mm from your spacer stack.