This is the Zipp Service Course SL-OS Stem with an adjustable rise. The Service Course SL-OS was designed for 1-1/4" steerer tubes, but with the included shims you can use the stem on 1-1/8" steerer tubes. Your stem has to resist flexing during sprints and accelerations, clamp securely to the fork and handlebar, and support your weight over significant impacts. It’s a difficult job, but the Service Course SL-OS stem is still able to combine strength, stiffness and reliability at a weight of only 135 grams (100mm). The Service Course SL's 3D-forged, 7075 series aluminum body paired with titanium Torx bolts delivers exceptional strength-to-weight ratio while allowing for smooth lines to complement the aesthetics of modern frames.