This Ritchey 1-bolt Carbon seatpost clamp kit is a fully equipped stock replacement kit for Ritchey 1-bolt Carbon Superlogic and WCS seatposts. They come in different clamp slot diameters to accommodate the larger diameter carbon rails found on contemporary saddle designs. The clamp kit includes the full carrier, main bolt, washer, one threaded and one un-threaded rail clamp. These clamps are designed to be used with Ritchey Superlogic and WCS Carbon 1-bolt posts only. The alloy versions require a different series of kits. One tip: Carbon post kits have a side plates with interior facing lower ridges, while the aluminum versions have smooth face clamp plates. Make sure to choose the correct rail size for proper fitment to your saddle.