The Uni Power Tank Pen and the Uni Power Tank Smart Series Pen have identical
ink cartridges. For some reason, unclear to me, the Power Tank refill and the
Power Tank Smart Series refill are not the same. The Smart Series refill
replaces the inner ink "tube" of the outer shell of the cartridge. This requires
quite a bit of manipulation. The end result, though, works just fine. The
Power Tank refill comes with the ink "tube" and outer shell together.
The main advantage of this refill is that it is a perfect replacement for the
mediocre refill (SJ-7) that comes in the Mitsubishi Pure Malt pen (SS2005). The
pen then becomes a well-balanced, great looking, and great writing pen.