Maybe it is a front shifter and rear tensioner so one could run a single cog freewheel in back and do the shifting between two chainrings in front. No flip-flop hub would required for the big climbs.
Steve Demchak Speculating in Sunny Seattle, WA
---------------------------------
Yahoo! Messenger with Voice. Make PC-to-Phone Calls to the US (and 30+ countries) for 2ยข/min or less.