The patented front suspension system found on all Cannondale bikes with front suspensions. It is a single shock on the steering tube instead of 2 shocks, 1 on each side of the fork. This gives better stability and turning ability. Some people love it (ie. me) and there are those that hate it. There is really no middle ground in that argument, it is whatever you are used to. Cannondale bikes however are the top mountain bikes in the world.