This is the best test-marking pen ever made. Even when my students write their
test in red, this pen is bold enough to stand out. I'd buy these in boxes of 10!
There is one minor concern though: A 1mm line means you'll run out of ink FAST.
Marking 90 tests uses just under half the ink, which is equivalent to writing
about 30 pages.
This is as good as it gets in a white pen. It's so opaque that I use it as a
whiteout pen! It writes a 1mm line, so if you need precision, you'll have to
look elsewhere. Otherwise, this should be your first choice in white.