Fisher Space Pen Bullet: Size, PR4 Refill & Claims

The Bullet closed, drawn to scale from Fisher's 3.77 in length.

Product facts

Product: Fisher Space Pen Bullet 400 (chrome)
Brand: Fisher Space Pen
Brand origin: United States
Made in: United States^*
Material: Chrome-plated brass cap and barrel, pressurized PR4 refill
Released: 1948^*
Price range: $$$$20–75 per pen (multi-packs divided by the count)

Notes on these facts

Made by Fisher Space Pen Co.. Made in United States: Fisher's own Bullet pages carry a made in USA notice, and GP Knives lists the country of origin as the United States. Wikipedia says the pens are manufactured in Boulder City, Nevada, and NASA's Spinoff describes Fisher as a Boulder City, Nevada-based company. Fisher's site and GP Knives refused our automated requests on October 20, 2026, so those two come from earlier reads and search snippets. Source. Price: example listing. Released: Retailer copy (Fountain Pen Hospital) says Paul C. Fisher conceived the Bullet in 1948; the pressurized cartridge it uses today came later, with Fisher's first AG7 patent filed on May 19, 1965, per Wikipedia. We found no dated launch from Fisher itself.
Price bands are typical US retail, checked October 2026.

Key takeaways

Fisher lists the Bullet at 3.77 in (96 mm) closed and 5.35 in (136 mm) open with the cap posted, so posting adds about 40 mm.
GP Knives lists the chrome 400 at 0.75 oz (about 21 g) and 0.39 in across; the body is chrome-plated brass.
It takes the pressurized PR4 cartridge, which Fisher and retailers say writes upside down, underwater and from -30 °F to 250 °F (-34 °C to 121 °C).
Retailer copy says Paul C. Fisher conceived the Bullet in 1948; NASA says Space Pens are in the Museum of Modern Art's permanent collection and entered the Space Technology Hall of Fame in 2021.
Fisher's product pages and US retailers list the United States as the country of origin; Wikipedia places the factory in Boulder City, Nevada.

What is the Fisher Space Pen Bullet?

The Bullet is Fisher Space Pen’s capped pocket ballpoint: a short, round-ended brass tube that grows to full length when you post the cap. The plain chrome model is the 400; versions with a factory clip add “CL” to the code, such as the 400CL.

Fountain Pen Hospital’s copy says Paul C. Fisher conceived the Bullet in 1948, years before his pressurized cartridge. Today it carries that cartridge, the same refill family as the AG7 Astronaut pen.

Fisher Space Pen Bullet specs

Spec	Value
Maker	Fisher Space Pen Co. (Boulder City, Nevada)
Type	Capped ballpoint, pressurized refill
Closed length	3.77 in (96 mm), per Fisher
Open, cap posted	5.35 in (136 mm), per Fisher
Diameter	0.38 in (9.7 mm), per Fisher; GP Knives lists 0.39 in
Weight	0.75 oz (about 21 g), chrome, per GP Knives
Body	Chrome-plated brass
Refill	Fisher PR4 (black medium included)
Made in	United States

Retailers disagree slightly on length: OpticsPlanet gives 3.75 in closed and 5.25 in open, and Lamnia 3.70 in and 5.375 in for a brass edition. We use Fisher’s own figures.

Closed and posted, at 1 mm = 4 px. Posting the cap adds about 40 mm.

How does the Bullet’s pressurized refill work?

The PR4 cartridge holds thick ink behind a sliding float, with compressed gas pushing on the float, so the ink doesn’t rely on gravity to reach the ball. Wikipedia describes the gas as nitrogen and the ink as thixotropic, a gel that thins as the ball turns.

Wikipedia gives the pressure as nearly 45 psi (310 kPa), while some retailers have said about 35 psi. Fisher hasn’t published a figure in the sources we could reach. NASA’s Spinoff adds that Fisher solved early leaks by adding resin to make the ink thixotropic.

Does the Fisher Bullet really write upside down?

That is Fisher’s claim: the pressurized cartridge is sold as writing upside down, underwater, in zero gravity and from -30 °F to 250 °F (-34 °C to 121 °C). Retailers repeat these figures, and Wikipedia gives −34 to 121 °C (about −29 to 250 °F).

We haven’t tested it. In practice the useful part is that it keeps writing on a wall, on a clipboard held overhead or on slightly damp paper.

Is the Fisher Bullet a good pocket pen?

Yes, on size: at 96 mm closed it falls inside the 89 to 114 mm range usually called a pocket pen, and posts to a normal 136 mm writing length. That’s why it appears in our best pocket pens roundup as the everyday-carry pick.

The plain 400 has no clip, so it rides loose in a pocket. If you want one, buy the 400CL or add Fisher’s separate chrome clip for 400-series pens.

How does the Bullet compare to other metal ballpoints?

It’s the shortest and only capped pen of the common metal ballpoints, and the only one with a pressurized refill.

	Fisher Bullet	Zebra F-701	Parker Jotter
Closed length	96 mm	133 mm	128 mm
Mechanism	Cap, posts	Click	Click
Refill	Fisher PR4 (pressurized)	Zebra F-Refill	Parker Quinkflow
Made in	United States	Indonesia	France

The F-701 is cheaper and full length; the Jotter is a click pen with a standard Parker-style refill. Choose the Bullet if you want the smallest pen that still writes in awkward positions.

Is the Bullet the pen that went to the Moon?

Not this exact model: the pen demonstrated on Apollo 7 in October 1968 was the AG7 Astronaut pen, which uses the same type of pressurized cartridge. NASA’s Spinoff site says Space Pens are also held in the permanent collection of the Museum of Modern Art in New York, and that the Space Foundation recognized the technology in 2021. Our best pens of all time guide covers the AG7’s history.

Where is the Fisher Space Pen made?

In the United States. Fisher’s Bullet pages carry a made in USA notice, and GP Knives lists the United States as the country of origin. Wikipedia says the pens are manufactured in Boulder City, Nevada, where NASA also places the company.

How much does a Fisher Bullet cost?

The chrome Bullet sits in our $$$ band ($20–75 per pen); Fountain Pen Hospital lists it at US$34. Special finishes and engraved editions cost more, and PR4 refills cost far less than a new pen.

Frequently asked questions

How long is the Fisher Space Pen Bullet?

Fisher lists it at 3.77 in (96 mm) closed and 5.35 in (136 mm) open with the cap posted on the back. Some retailers round these to 3.75 and 5.25 in.

What refill does the Fisher Bullet use?

The Fisher PR4, a pressurized ballpoint cartridge. GP Knives lists a black medium PR4 as the refill included with chrome Bullets, and Fisher sells it in other colors and point sizes.

Does the Fisher Space Pen really write upside down?

That's Fisher's claim for its pressurized cartridge, along with writing underwater, in zero gravity and from -30 °F to 250 °F. Retailers repeat it; we haven't tested it ourselves.

Does the Fisher Bullet come with a clip?

The plain 400 has no clip. Fisher sells a 400CL version with a clip already fitted, and GP Knives lists a separate chrome clip for 400-series Bullets.

Is the Fisher Bullet the pen astronauts used?

Not exactly. NASA says the Space Pen's TV debut was on Apollo 7 in October 1968, and Fisher's first space model is the AG7; the Bullet uses the same type of pressurized cartridge in a pocket body.

Where is the Fisher Space Pen made?

In the United States. Fisher's Bullet pages carry a made in USA notice, GP Knives lists the US as the country of origin, and Wikipedia says the pens are made in Boulder City, Nevada.

How heavy is the Fisher Bullet?

GP Knives lists the chrome model at 0.75 oz, about 21 g. A raw-brass edition is listed by Lamnia at 19 g.

Sources (9)

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