While researching the findings of others, it seemed that few folks had pursued alternative pen bodies for the Montblanc fineliner refills. However, a number of internet forums had discussion threads in which the participants spoke about searches for alternative pens to take the Montblanc rollerball refills. One popular option, reported to be successful, was the Waterman Kultur rollerball pen, as well as some Jinhao pens (but not all of them). By far the most popular was a hack in which one cuts some of the plastic from the non-tip end of the refill, shortening it, so that it may fit inside a Pilot G2 body. Inexpensive, mostly comfortable in a utilitarian way, and easy. I loved the idea.
Then, during my last trip to Montblanc, I learned that the rollerball and fineliner refills are interchangeable. This was the breakthrough. While this compatibility may be obvious, if the refills were inspected side-by-side, I had not yet been able to do so. Immediately, I purchased a pack of fineliner refills and sat down (not in the store) to perform the G2 hack on a fineliner refill.
Here you can see a comparison of a G2 refill (top), the modified fineliner refill (middle), and an unmodified fineliner refill (bottom):
All that it took to modify the fineliner refill was cutting some of the plastic from the non-tip end. Simply line up the tip-end of the main body portion of a G2 refill and the fineliner refill and see how much overhang is on the non-tip end of the fineliner refill. That will show you how much to cut.
My new, inexpensive fineliner was fantastic. I quickly determined, over several days of use, that the fineliner was second only to fountain pens in my mind. However, the G2 body quickly became unsatisfactory to me. I wanted something nicer in which to case a fineliner refill, hacked or un-hacked, without spending a large amount of money.
Knowing that the hacked refill fit a Pilot G2, I began to investigate what other pens took a Pilot G2 refill. Then, I remembered one of the recent, inexpensive entries to the fountain pen world: the Pilot Metropolitan. Since the Metropolitan was available in a rollerball variant, I ventured a guess that it might take a Pilot G2 rollerball refill.
I was right.
Swapping my hacked fineliner refill for the refill from the Metropolitan, I was left with something awesome: the great writing experience of the fineliner refill combined with the comfortable - and affordable - Pilot Metropolitan body.
If you are looking for an alternate body for using the Montblance fineliner refill (or even the Montblanc rollerball refills), look no farther than the Pilot Metropolitan and this easy hack.