The Atomic Bear carries Schmidt, Fisher Space Pen, and Parker G2-compatible tactical pen ink refills — each one tested for exact fit in our pen lineup. No guessing, no trimming cartridges to length. Pick your pen, pick your refill, done.

Every Atomic Bear tactical pen except the MTP-6 accepts Parker G2-format cartridges. That means the following EDC pens all take the same refills:

• Guardian Titanium
• Guardian Titanium Noir
• SWAT Pen
• REBEL Pen

The MTP-6 uses the shorter Schmidt P950 Megaline pressurized cartridge.

Need a pressurized refill that writes at any angle, in cold weather, or on wet paper? Go with Fisher Space Pen. Want the smoothest everyday ink line? The Schmidt 9000 EasyFlow is what ships with the Guardian Titanium for a reason.

Not sure which pen to pair with? Read our guide on the best tactical pens: tested & compared that breaks down every model.

See also our tactical pens and Fisher Space Pen Refills.

Frequently Asked Questions on Tactical Pen Ink Refills

Can I put a 0.5 refill in a 0.7 pen?

Yes. The 0.5 and 0.7 refer to the ball diameter at the tip, not the cartridge size. As long as the refill format matches (Parker G2 in most cases), both fit the pen identically. The only difference is line width.

Do pen refills fit all pens?

No. Refills come in specific formats — Parker G2, Megaline, D1, and proprietary sizes. Most Atomic Bear pens use Parker G2. The MTP-6 requires the shorter Schmidt P950 Megaline. Check which pen you own before ordering.

How many times can you reuse a cartridge?

Cartridges are single-use. The ball-and-socket tip is precision-manufactured and cannot be reloaded without compromising ink flow. Our refills are sold in 2-packs to keep you stocked.

What is the difference between a pressurized and a standard pen refill?

A standard refill relies on gravity to feed ink to the tip — works great at a desk or in normal conditions. A pressurized refill (like Fisher Space Pen) uses a sealed nitrogen chamber that pushes ink regardless of angle, temperature, or altitude.

Pressurized writes upside-down, in freezing cold, and on wet surfaces. Standard gives you a smoother, more fluid line for everyday writing.