The Speed Force II is Xero's lightest shoe, the closest thing they make to a racing flat: a thin FeelTrue rubber sole, a zero-drop platform, and adjustable straps holding your foot down. It is barely there, and with no midsole foam to break down it lasts far longer than that suggests.
It suits you if you already run in barefoot shoes and want a stripped-back option for the sharp end of the week — strides, intervals, short tempo work, and a 5K if your feet have earned one.
It is not a shoe to build mileage in. There is nothing under your foot to absorb a bad landing, so first sessions should be short and forgiving. It is not a super shoe either: no plate, no stack, no free speed — everything it gives comes from taking material away, which only helps once your feet and calves carry that load.