FSA's OS-150 Stem is a worthy upgrade for your favorite bike. It's made of forged and CNC-machined aluminum, so it's light, durable and strong enough for any road or mountain riding adventure.
Stem length is measured along the side of the stem from the center of the steerer to the center of the handlebar clamp (see diagram). Keep in mind that as a stem provides more rise, its effective length decreases. In the example above, if the +17-degree stem measures 135 mm, it actually extends 108 mm parallel to the ground.