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FSA OS-99 Stem


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OS-99 Stem

Let's get one thing out of the way—the OS-99 Road Stem is the lightest stem that FSA makes, and no, the "7050 aluminum body" isn't a typo. By using a proprietary 3D forging technique and special heat treatment ("witchcraft" is the technical name) FSA makes the OS-99 as strong as a heavyweight stem but as light as a part made of pure carbon fiber. To be fair, the faceplate is built partially from carbon, to achieve the perfect balance of strength and weight, and the unbreakable bolts have been forged from titanium, so the OS-99 isn't pure aluminum. The faceplate also has a serrated surface that will grip both carbon and aluminum bars, and a rise of +/- six degrees, depending on which way you set it up.

  • 7050 aluminum body
  • Titanium bolts
  • Alloy and carbon faceplate with serrated grip surface
  • 31.8mm clamp diameter
  • 1 1/8in steerer tube diameter
  • +/- 6 degree rise
  • Item #FSA000I

[body] aluminum, [bolts] titanium, [faceplate] alloy/carbon
Clamp Diameter
Steer Tube Diameter
1 1/8in
Bar Attachment
Claimed Weight
[90mm] 3.6oz (103g)
Recommended Use

Tech Specs

What do you think about this product?


>Rating: 2

FSA OS-99 stem

I purchased this stem a few months ago. I like the mat flat finish, however, when properly torqueing the pinch bolts, the ears of the stem are touching. This despite under torqueing to only 4nm not the 6 recommended that I have never torqued to. Before you tell me to look more closely I actually put a piece of paper between the ears and couldn't remove it after tightening the pinch bolt. Expensive and certainly not thoughtfully engineered.


hello, do you have actual weight on the...

hello, do you have actual weight on the FSA OS-99 stem? And any other stem comparable to this one you'd recommend? thanks very much