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 weightDesign allows adjustments to be made with one easily accessed horizontal bolt1-piece shaft and cradle supportSideBinder clamp uses a single 5mm bolt to secure the saddleWide saddle clamp reduces stress on lightweight saddle railsWorks with all saddles with available clamp kits (ST3280 ST3281)