It is possible to change the weight or balance of a fountain pen according to the user's hand writing. Nakaya has been studying this problem for a long time and after much research and trial and error, Nakaya "The Equilibrium Balance control model" was born. It has a mechanism called "Weight Ring" where one or more metal rings could be inserted into the pen. This model has an internal spiral thread along the whole of the internal barrel. Several weight rings could be set at any position inside the barrel so as to achieve the desired balance needed.
Five weight rings are initially supplied with the pen. The maximum supported rings that could be inserted in the pen are ten. In the portable size model nine rings could be inserted.
If you would like more rings, it can be ordered separately.