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Full Speed Ahead OS-99 CSI Stem

The OS-99 CSI (Carbon Structural Integration) is FSA's version of a carbon matrix stem. They start with a thin 3D net forged alloy core and wrap 3K carbon weave around the core to assemble the body of the stem. This process yields the strongest and stiffest stem with minimal weight gain. The added stiffness offers the rider near perfect steering input. The carbon wrap not only provides strength, but excellent road dampening as well.

The carbon wrap is 3K weave, which means it looks like carbon fiber, unlike UD carbon which look more like a sheet of carbon. Familiar red and white strips with FSA logos adorn the side of the stem. The OS-99 CSI stem body and face plate are both coated with a gloss finish that is durable, prevents corrosion from perspiration and cleans up easy after use.


  • Forged and CNC-machined 7050/T6 alloy core
  • 3K carbon wrap
  • High gloss finish
  • Carbon wrapped and sculpted 4-bolt faceplate
  • 6/4 Titanium hardware
  • 84º rise
  • 31.8mm handlebar clamp diameter
  • 35mm stack height
  • 118 gram
  • $129.00
    Reg Price $164.95
    Item #: 326150 Weight: 118g