The ExtraTerrestrial is a 700c tyre with a very directional tread that offers a great balance between decreased rolling resistance and reliable traction.
It shines on hardpack surfaces giving you plenty of traction in corners and on off camber stuff. The ET would be at home doing a long distance tour in S. America, or a pedal from S. Minneapolis through the River Bottoms.  
We found it to be a good commuter tyre as well, especially if your commute takes you on mixed surfaces.
 
Casing: 60tpi
Tubeless Ready Bead: The bead design is intended to interface with the bead hook on Surly, Whisky and similar rims for tubeless applications.