This is Jetstream Ballpoint Pen Ink Refill for the Uni Style Fit multi pen in a 0.5 fine point.
Pen bodies are available for purchase separately here.
Featuring Jetstream ink, which is a hybrid ink that combines the great qualities of a ballpoint ink and a gel ink into one. This pigment based ink boasts the following qualities:
low-viscosity
smooth writing
quick drying (great for left handed users)
waterproof when dry
fade and forgery resistant
clean and vibrant color compared to other traditional ballpoint inks