The CG-R seatpost extends the concept that “ Smoother is Faster.” This revolutionary post features 18mm of vertical compliance Zertz vibration damping & FACT carbon construction. The CG-R delivers unsurpassed comfort control & efficiency without adding weight or complication to the frame. No matter what surface your ride takes you on the CG-R will make it better. Revolutionary design allows 18mm of vertical compliance.FACT carbon construction blends durability & comfort. Vibration-damping Zertz for increased comfort. Cylindrical aluminum head assembly adjusts fore-aft & tilt with an easy-access single bolt. Diameter: 27.2mm