Zipp's Service Course SL seatpost is specifically tuned to be more shock absorbing than the comfort seatposts on the market, while still passing our strict internal MTB strength test. Updated distinctive Zipp cosmeticsUnidirectional carbon construction is tuned to give a smooth, compliant ride400mm length suitable for compact road and gravel framesSaddle clamp works with round and oval railsFlex 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 redesigned for maximum bolt head accessibility. The saddle clamp also works with regular round and oval carbon saddle rail types. If you want a lightweight, smooth riding carbon seatpost that will stand the test of time, the Zipp Service Course SL is a great choice!