The stationery community has been writing a few Retro 51 articles on stationery.wiki. When I tried to make the information in these articles semantic I came across a few issues.
One issue is related to Retro 51’s refills, one related to their categories, lines and editions. Luckily the users in The Pen Addict’s Slack channel are extremely helpful and knowledgeable when it comes to Retro 51 so the confusion with Retro 51’s series, categories, lines etc has been solved.
The other issue, relating to their refills, took me a while to figure out. This was probably not helped by the fact that I don’t own a Retro 51.
The short answer is: I think Retro 51’s rollerballs accept standard G2 refills, which means you can turn them into rollerball, gel or ballpoint pens.
Here are some of the bits of information I found along the journey. They might be old information for you, but since I am more into pencils and fountain pens than refillable non-disposable rollerballs a lot of this was new to me.
Refills are standardised in the ISO standard 12757.
ISO 12757-1 is for general use, i.e. there are not too many demands on the ink.
ISO 12757-2 is for documentary use, i.e. for writing documents that are required as evidence and the standard also looks into things like how the ink is coping with bleach, etc.
There seems to be contradictory information on the web when it comes to the G2 refills. This is probably not helped by the fact that Pilot has a pen called the G2. Based on what I have seen so far G2 and RB refills tend to get confused.
The G2 standard seems to have its origin in Parker’s Jotter refills, which came out in the 1950s.
I have produced a little table with further information about these refills. It also includes average writing length per refill based on the information by Premec. Other refills may vary.
|Type||Diameter||Length||Name||Avg writing length||Ink charge|
|2.35||57.1 or 67.0||multicolor|
|350 m||0.1 g|
|Japan Style||2.9-3.0||variable||600 m - |
|0.22 g - 0.32 g|
|Spezial||3.0||61.0 or 66.5|
|1700 m||0.375 g|
|G2||6.00||98.1||ballpoint / gel |
400 m (gel)
5000 m (oil based)
|0.7 g (gel)|
1.1 g (oil based)
|RB||6.30||110.0||standard rollerball||0,5 mm: 500m|
0.7 mm: 400m
|gel refill||0.7 mm:|
450 m (stick)
600 m (retractable)
|0.7 g (stick)|
0.9 g (retractable)
For more information about refills see The Well-Appointed Desk’s Epic Refill Reference Guide and The Refill Finder.
The diagram is from Qniemiec, translation by Francis Flinch and is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.