The FSA OS-99 CSI Stem is the OS-99 alu stem, wrapped in carbon.
Before the OS-99 gets wrapped in carbon, the stem first goes through a 3D forging process, where the aluminum molecules transform into a useful product (aluminum). It’s then CNC machine carved from a single aluminum block. A 3K-carbon weave skin is then applied through a CSI (Carbon Structural Integration) process. This CSI process makes the two materials one and permanently bonds them together. This allows you to reap the benefits of both materials.
The OS-99 CSI Stem uses a 4-bolt, alloy/carbon faceplate and titanium hardware to keep the weight low (122 grams at the 110mm length). The 4-bolt design disperses the clamping pressure evenly over the bar.
The FSA OS-99 CSI Stem weighs just 122 grams for the 110mm length and is also available in 80, 90, 100, 120 and 130mm lengths. It uses a 31.8mm handlebar clamp.
FSA OS-99 CSI Stem Details
Angle: +/- 6 degrees
Stack Height: 40mm
Weight: 122grams @110mm
Steerer: 1 1/8”