The habaki is the piece of metal circling the base of the blade. It has the two main purposes, locking the tsuba in place, maintaining the sword in the Saya.
Unlike Shinken Habaki, that can be incredibly expensive, Iaito Habaki are standardized and gently forced in place. This means that it is not recommended to remove/change the Habaki on a Iaito blade.
Habaki are made of brass and available in two different design, standard and Shonai (antique design) and 3 different finishes, black (oxydized), gold plated and silver plated. Note that due to the oxydation process, it is not possible to blacken the Shonai design.
The seppa are washers used in front and behind the tsuba to tighten the fittings, made of copper. They are mandatory to keep the Tsuba in place securely.
They are available in black (oxydized), gold plated and silver plated.