This prologo zero ii pas nack saddle is a lightweight flat saddle designed for the road xc or mountain biking racers with nano carbon nack rails which are a mixture of carbon fibre kevlar and aluminium filaments in the seatpost clamp area then the rails are treated to a production process called braided carbon rail the result is a balance structure and resistant to penetration on top of the rails is a light and strong carbon injected base with light pu padding combine with the pas technol