These are my favorite...
, February 13, 2014
These are my favorite refills to use in my Frixion Biz pen, which I frequently
employ for lengthy math-work sessions. These are deliciously smooth refills
with a brightly pigmented blue ink, and they make a satisfying medium-width line
on the page without being overly bold or inky. Dries fairly quickly (3-5
seconds at most) and erases completely clean. These refills also never skip and
always start up easily when you need them to. My only complaint is that the ink
gets used up quickly due to its semi-viscous nature and 0.7 mm tip. The overall
writing experience is so good that I don't mind paying a bit extra for all of
the refills that I go through.