Titanium Pen Refill Guide
Refill Guide: Titanium Bolt Action Pen
You went with Grade 5 titanium for a reason. The right refill keeps the writing feel as precise as the pen.
This page covers exactly what fits the Titanium Bolt Action Pen by Bastion®, what doesn't, and how to swap the cartridge in under a minute.
The short answer
Your Titanium Bolt Action Pen takes a classic Parker-style G2 refill, sometimes called an "ISO G2" or "International G2" cartridge. The official spec is roughly 98mm long, 6mm wide, with a tapered front end and a 0.55mm fine tip.
Bastion's own replacement cartridges are made to that exact spec, so they're the safe bet. They come in:
- Standard ballpoint, black, blue, red
- Gel ink, black, blue, red
- 0.55mm fine point
Shop Replacement Ink Cartridges
What "Parker-style G2" actually means
Parker-style G2 is an industry standard, not a single brand. Several pen makers produce cartridges to this size. The keyword is classic. Parker and a few others changed their cartridge body width sometime after 2015, and the wider versions don't always seat properly inside a precision-machined bolt action barrel.
If a refill is sold as a "Parker-style G2" or "ISO G2" with the tapered front end, it's almost always going to fit. If it looks like a straight tube with no taper, or it advertises a body wider than 6mm, it probably won't.
What does NOT fit
- Pilot G2. Different cartridge entirely, despite the matching name. The Pilot G2 is a Pilot-proprietary refill and won't seat in your Bastion pen.
- Wider-body Parker refills made after 2015. These can stick or fail to retract.
- Schmidt P900-style "Parker-G2" branded refills are usually fine if they're tapered, but check the dimensions before you buy a pack.
When in doubt, our team can confirm before you buy. Email or use the chat in the bottom right.
How to swap a refill (under a minute)
- Open the bolt by sliding the rear bolt forward and to the side (locked open).
- Unscrew the front tip section by rotating it counterclockwise.
- Pull out the old cartridge and the spring (set the spring aside, you'll reuse it).
- Slide the spring onto the new cartridge.
- Drop the cartridge spring-end first into the barrel.
- Screw the front tip back on, snug but not over-tightened.
- Slide the bolt back to closed. Test on paper.
If the new cartridge feels stuck, doesn't retract, or scratches the paper, the refill is the wrong size. Pull it back out and try a Bastion replacement.
What real Bastion owners say about the Titanium pen
"Excellent craftsmanship. My new fav!" Henry Kotowski, 3/27/2026
"A pleasure to hold and write with!" Andrew D, 3/25/2026
Titanium pens stay in your pocket for years. The right refill is what keeps the writing pleasure consistent.
Pen specs (for reference)
- Weight: 1.6 oz
- Length: 5.25 inches
- Closure: Retractable bolt action
- Material: Grade 5 Titanium (Ti-6Al-4V), natural finish
- Point type: Fine (0.55mm)
- Refill standard: Classic Parker-style G2 / ISO G2
Need a fresh refill?
Bastion replacements ship from our warehouse. Standard ballpoint or gel, black/blue/red, $6.99. Free shipping over $35.
Shop Replacement Ink Cartridges | View the Titanium Pen
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