This is a bottom assembly only. It comes in a special irregular size! The technical details are ZS/55/40/H4/K Bottom. It's a ZS - ZeroStack type with a crown race seat diameter of 39.79mm. The crown race is made of steel and face - sealed. The bottom bearing is black oxide and sealed, and the material is 6061. The part number is BAA0737K. The all - new 40 - Series is the workhorse of Cane Creek’s headset line - up. It combines all features for a durable, lightweight, and long - lasting headset, offering the perfect balance of performance, durability, and value. Precision engineered in Fletcher, NC. Key features include 6061 - T6 aluminum cups and covers that are internally relieved to cut weight. The innovative Clip - Seal seals the top assembly and holds the compression ring, reducing loose parts. High - quality, low - friction face - seals are on the crown races. The durable steel crown races and dependable black - oxide, sealed cartridge bearings ensure great performance.

Using this Cane Creek 40 - Series bottom assembly is straightforward. First, make sure your bike is compatible with the 55mm 1.5in crown race size. Install the assembly carefully following the general bike headset installation steps. When it comes to maintenance, regularly check the seals. If you notice any dirt or debris around the seals, clean them gently with a soft cloth. For the bearings, it's a good idea to have them inspected every few months, especially if you ride frequently. Avoid using harsh chemicals on the assembly as they can damage the materials. Also, store your bike in a dry place to prevent rust and corrosion on the steel crown races and other metal parts.