Bontrager's SSR 4-Bolt Stem is made of forged 6000 aluminum for awesome strength. The 4-bolt faceplate makes it super easy to install and distributes the clamping force on your bars.
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.