Recently I purchased a bunch of pen refills to improve some pens I 
have some 80-90s era IBM pens that just had dried up plastic stick 
as well as some other more modern pens I like the appearance of, bu
crappy refills.

First I have some Chinese knock offs of nicer pens that took roller
refills. Pilot G2 style refills will also fit so I put an Energel 0
Sarasa Dry 0.5 refill. The Sarasa Dry is impressively dark and whil
does dry fast, it has a very wide line for 0.5 and seems splotchy.

I also bought a Pilot Multiball rollerball pen to compare to the Pi
Precise. It seems okay, the 0.5mm Multiball writes scratchy compare
the Precise V5. I guess it has the advantage of being able to write
non-porous surfaces. I also bought a Uni Boxy 100 which is very coo
pen but the refill that comes with is very poor ballpoint ink. It's
very dark and has a lot of resistance. I put a 0.5mm Jetstream mult
refill in it. It fit, I just had to add some scotch tape in the rig
place as a spring stop.

Now onto the real modifications. I have this cool looking IBM Print
Systems Division pen that has a cylinder with text on it and two wi
on the outside. Every time you click it rotates through the text. I
to put a Hi-Tech-C 0.3 blue multipen refill in it, but had issues g
the spring top in the right place and accidentally popped the tip o
which messed up the refill and put an air bubble in it, I might be 
to fix it later, but it will be a messy job. So instead I managed t
a Zebra JK 0.7mm ball point refill in it. I had to pop the back cap
the refill so it would fit in the tube with the writing and then sh
with a lollipop stick it works  but it doesn't have a nice feel to 

Next I had a fancy looking IBM twist pen that uses cross ball point
I didn't like any of the compatible refill choices so I decided to 
Ohto needletip ballpoint refill that was very close to the correct 
I had trimmed a few mm off the back of the Ohto refill then moved t
cap over from the back of the cross refill to the Ohto. After that 
discovered the spring stop on the Ohto made it too wide to fit so I
those down. Then I found that the upper part of the tip was too wid
through the front of the pen so I drill it out a bit and filed it s
It works great now and I really like the Ohto needle ballpoint. The
are very precise and it lets me write smaller than the Hi-Tech-C 0.
with it being 0.5mm. Will certainly always want to have a pen with 
refill around.

The final of the IBM pens is this one from a charity drive in 1990.
the triangle shape to be very comfortable in the hand and I like th
and blue colors. I decided to put a 0.4mm Hi-Tech-C multipen refill
in it. The spring stop on the new refill was in the right spot, the
just needed to be longer. So I cut a piece of dried up stick refill
laying around to be the correct length as a spacer. I found when I 
the clicker the refill and the spacer didn't always align so I join
with scotch tape. Works perfect now. Despite liking using the full 
Hi-Tech-C pens for diagrams I am disappointed with this vs the Ohto
needlepoint. Despite being a smaller tip, the line is larger and I 
write  as small. I also do have be careful not to touch the ink aft
writing or it  will smudge. All this makes sense as it is gel. I pr
Ohto although it doesn't  come in colors. The Hi-Tech-C is cheaper 
Ohtos but given Ohto is ballpoint it may last long enough vs this g
refill to be worth the extra expense. 

Last but not least, I decided to change the ink in the two Zebra G-
have. I think these pens look great, but I regret getting the G vs 
series. The gel refills are splotchy and easy to smudge. And I've r
don't last long because of their size. I decided to replace these w
a black and blue Acroball 0.5mm multipen refills. I have tried 1.0m
before and thought it dried too slow, but I do like it in 0.5mm. It
ALMOST as smooth as Jetstream. To get them to fit, I had to cut abo
off the back and use scotch tape as a spring stop. 

Finally here is a photo of a writing sample with all the "new" pens