When the ink in the pens went running out, I bought the Copic ink for refilling, plus the Copic replacement nibs.
One notices a difference, mainly because the points are a little harder and the color does not run. The Alpha-markers the transitions were from time to time something "frayed" and indistinct.
I was very satisfied with the purchase and would buy again at any time ... Therefore, a clear recommendation.
One star deduction however, there is still, as the ink just sometimes blurred and the tips are quickly very soft and therefore no clean lines are guaranteed. But through the refill products Copic the pins can be significantly upgraded.