Cervelo SP18 Zero Setback Seatpost - SP-SP18-ZEROCervelo introduced their Squoval Max tubeset with the 2018 R5. The more aerodynamic tubes feature a D shaped or flatback seattube, hence the development of a UD carbon flatback shape seatpost, the SP 18 Carbon Seatpost. Cervelo offers the two bolt fore aft seatpost head as a separate item. This is a post only no head. Cervelo requires 70mm minimum insert for safety, which is clearly marked, as is the adjustment scale for accurate installation, fit,