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FSAOS-99 Stem


Item # FSA000I

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  • Black, 100mm ($174.00)
  • Black, 60mm ($174.00)
  • Black, 120mm ($174.00)
  • Black, 130mm ($174.00)
  • Black, 80mm ($174.00)
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Item # FSA000I

Bantam-weight brawler.

FSA manufacturers carbon fiber stems, but arguably its very best stem (though not the most exotic or the most expensive) is the OS-99. The OS-99 is the lightest stem in the FSA family and — believe it or not — it's made from 7050 aluminum alloy.

Don't let the extreme lightness of the OS-99 give you concerns about durability. FSA manufactures it using a proprietary 3D forging technique that uses slow forging speeds and extremely high pressures to eliminate surface deformation. It carefully controls the heat treatment process to ensure ideal crystal growth. The heat treatment is so critical to the finished product, in fact, that FSA documents and inspects every heat treatment session to ensure quality. It might be exceptionally lightweight, but it has the toughness of a heavyweight.

The forged faceplate has a serrated grip area to securely fix both alloy and carbon fiber handlebars. All sharp edges are radiused to eliminate potential stress risers — even the washers and counterbores for the Ti bolts are radiused for better stress flow. And the clamping area is diagonally cut to better distribute the clamping load across the steerer tube.

The OS-99 is available in six lengths, from 80mm to 130mm. It has an 84 degree rise (+/- 6 degrees), with a clamp stack height of 41mm. The clamp diameter is 31.8mm.

  • 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

Tech Specs
Material[body] aluminum, [bolts] titanium, [faceplate] alloy/carbon
Clamp Diameter31.8mm
Steer Tube Diameter1 1/8in
Bar Attachment4-bolt
Recommended Usecycling

Actual Weight

Black, 100mm
Black, 60mm
Black, 120mm
Black, 130mm
Black, 80mm

Claimed Weight

Claimed weights are provided by the vendor.

Have questions? Chat with a Gearhead

[90mm] 3.6oz

Actual weights are measured in-house by the Competitive Cyclist team.

Have questions? Chat with a Gearhead

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