Ritchey WCS Carbon 1-Bolt Seatpost: 31.6 400mm 25mm Offset BlackRitchey WCS Carbon 1 Bolt Seatpost: 31. 6 400mm 25mm Offset Black. Ritchey WCS Carbon One bolt. Head uses less aluminum than other designs resulting in reduced weight. Head uses less aluminum than other designs resulting in reduced weight Design allows adjustments to be made with one easily accessed horizontal bolt 1 piece shaft and cradle support SideBinder clamp uses a single 5mm bolt to secure the saddle Wide saddle clamp reduces stress on