The Seppa are small metal washers that are placed on each side of the Tsuba in order to absorb the shocks, but also to reinforce this part of the nomenclature.
But beware! It is not for that reason that it is a detail which is not worked. In fact there are many shapes, materials and types of Seppa. Often the traditional style of Seppa is recognized by a round with teeth.
All about Seppa
Manufacture and price
Seppa are usually made of copper or brass, these materials allow a unique absorption of blows without damaging the elements of the nomenclature that are in contact with the Seppa.
Rarer materials like silver, gold or even leather can be found, but this is much rarer. This part of the nomenclature is quite cheap, it costs about $5 for a pair of Seppa if this pair is made in a factory with a machine.
On the other hand, if we talk about a pair of Seppa imported from Japan and made in Japan, you have to count at least $30 and this price can go up to more than $300 if this pair is custom-made in the best materials.
The problem is that the Seppa can be ill-fitting to the nomenclature or have a little play. That's why some people opt for custom-made Seppa to fit the Tsuba perfectly.
So be careful when you change Tsuba for example to check that the Seppa fit well with the nomenclature. If not, you can try to fill the gap with another pair of Seppa.