Ritchey WCS 1-Bolt Seatpost: 31.6, 400mm, 20mm Offset, BlatteThe Ritchey WCS 1 Bolt Seatpost features the patented SideBinder clamp desing that uses a single 5mm bolt for quick, secure adjustment. SideBinder clamp uses a single 5mm bolt to secure the saddle Wide saddle clamp reduces stress on lightweight saddle rails Works with all saddles with available clamp kits (ST3282, ST3283) Item Specifications Clamp Style Standard Rails Color Blatte Defined Color Black Diameter 31. 6 Length 400 Material Aluminum Offset