Zipp Service Course SL Seatpost, 0mm Setback, 25.4mm Diameter, 400mm Length, Matte Black, C2The carbon Service Course SL seatpost is specifically tuned to be more shock absorbing than the "comfort" seatposts on the market. Flex engineered into the lightweight carbon tube keeps the rider comfortable over any terrain. Better fit means better performance, and if your saddle is out of position, you'll waste energy with every pedal stroke. The secure, two bolt clamp makes for easy micro adjustments of saddle position, and the head has been