For this world class stem Zipp uses unidirectional carbon and borrowed the Exogram technology that SRAM uses for their high end cranks for a stem that is exceptionally stiff while remaining incredibly light. Stiff and light is easy enough to claim but Zipp has crunched the numbers and tells us that the SL Sprint delivers an off the chart 1.8 grams per newton meter of stiffness more than stiff enough even for the sprinters of the pro peloton. The shape of this stem right down to the included top cap is also designed to let air flow right around it so nothing is lost by its aerodynamics either.