I came to conclusion that these color refill sticks along with the red ones are
the best there is (apparently Staedtler and Faber Castell 0.5 mm blue leads are
the best but I cannot find where to buy) when it comes to color pencil refills.
They break less easily as compared to color sticks from Uni and Pilot Eno (lets
not forget these are not graphites so offcourse they will break easier than
graphite sticks) but, MOST importantly the color from these sticks does not
disappear overtime as it does with Pilot eno color sticks. This maybe of
importance to artists as you may not see your color lines in a few weeks or
months (I cannot see preliminary drawing lines I did few weeks ago with color
Pilot eno light blue sticks but i see no changes in color strength with these
blue or red pentel pencill refills). Offcourse this may be not important to
some, depending on your needs.