(company page, on Wikipedia)
store on penloversparadise.com
https://web.archive.org/web/20170919123714/http://global.kyocera.com:80/prdct/fc_consumer/stationery/index.html

These are high-quality pens which use ceramic-tipped water-based refills.

Much of my writing is pen and paper, and the right pen is extremely important. A certain balance, texture and weight of pen, and a smooth writing experience are important to me. Put one of these pens down on a table, and spin them. They spin around the central closure for when the cap fits against the pen. That's Japanese quality.

I've bought these from ThinkGeek ^[ 1 ] was at www.thinkgeek.com/product/edb0/ , but most recently I'm buying them from penloversparadise.com.

I do not know if this ink is archival quality!

Refill variations ∞

Thin executive pen, bronze

Summary: Don't worry!

Pay attention to these things:

1. The "300 series" is what you want.

   • 300, 305, 307 or whatever you may find.
   • I'm told that the C-300 series refills will also fit in pens which use the Otho refills. If so, the reverse is probably true.
   • There are a number of forum threads floating out there which go over which pens can use which refills. I'll leave that as an exercise for the reader.

2. The mm tip width. Any refill tip will fit. Choose your preference

   • I have seen 0.5mm and 0.7mm

3. The ink colour.

   • I have seen black and blue. Red might be available, but so far I've only seen it with the Kyocera ceramic-tipped disposable pens.

• C-300 2L - 0.5mm black refill, source unknown.
• C-300 3H - 0.5mm black refill. Bought separately.
• C-300 4D - 0.5mm black refill which came with both the blue and silver thin executive pens.

• C-307 3D - 0.7mm blue refill. Bought separately.

From what I can tell, the C-300 2L, 3H, 4D are all exactly the same.

I bought the "C-305" from penloversparadise.com and received the C-300. They are the same.

--

Drop-in replacements:

• OHTO Ceramic 0.5mm Ballpoint Pen Refil, Black (C305-Black)

Possible alternatives ∞

Unknown:

• Schmidt easyFLOW 9000

  • https://www.amazon.com/dp/B0025ZX11S

• Ohto C-305P

  • https://www.jetpens.com/Ohto-C-305P-Ceramic-Rollerball-Pen-Refill-0.5-mm-Black/pd/822

• D1 Multipen Refills

  • https://www.cultpens.com/c/q/explore/product-type/refills/d1-multipen-refills

The blue pen's true colour ∞

Note that the blue pen is much darker than images show. Mine almost black, almost green and is more toward a hematite than blue. It's beautiful, and I'm glad I disregarded my hesitation and bought one.

Gallery ∞

Thin executive pen, bronze

Thin executive pen, blue. The pen is much darker than this image.

Thin executive pen, silver

C-300 or C-305 0.5mm black refill