Pen Refill Guide | Sharpen (2023)

Unsharpen may earn a commission when you make purchases through links on our site.

Pen refills come in a variety of shapes and sizes. Some of them are standards, common to pen brands and decades of pen designs, while others are appropriate and limited to only a few brands or even a few models. This means that replacing the ink in a pen, especially an older one, can end up being a more difficult task than you might expect.

The goal of this article is to make buying a new ink refill for your pen as easy as possible. A secondary goal of this guide will be to increase the number of refill options available for each pen. This is only possible if you have a good understanding of which types of filling and which are interchangeable.

Contents show

ISO standard for refilling the pen

Many pens meet the requirementsISO standard 12757and the later revision of ISO 12757-1:2017 by the International Organization for Standardization. This is not something that is mandatory - custom and proprietary fillings are certainly not illegal - but for practical reasons, if you are making a certain type of filling, it makes sense that yours should have the same dimensions as other manufacturers' fillings.

Subscribe to YouTube

The standard has two main components: one for general use and one for "documentary use", which is basically a stricter standard. The latter application is ISO 12757-2 and covers readability of fonts as well as writing for archival documents.

Comparison of refills for ballpoint pens

Here is a visual representation of some of the many ISO standard pen refills. It mainly shows ballpoint pens, but rollerball, gel and hybrid pens can also have these shapes.

Reading the diagram:

The far left column of the image is the diameter of the refill in millimeters. E.gD-6,00means that the filling is 6.00 mm in diameter.
The circled element is the name.G2is the name of a specific refill specification for a pen.
Next is the length in millimeters.L=98,1meaning it is intended to be 98.1 millimeters long.
Finally, there is a top-up picture in the profile. A true technical drawing of each charge would have many more measurements as there are very exact specifications for each charge, but it will give you an idea of what each charge looks like.

This can be used as a handy visual guide and will be useful if you happen to have a charge that you cannot identify.

ISO standard refill types for ballpoint pens

Here are some popular ISO compatible refills with an explanation of each.

D1 supplement

Format D, better known as D1, is a small cartridge commonly seen in multi-pens andmini pencils. Unlike some of the other standards on this list, the D1 remains a very popular cartridge to this day. D1 refills are usually metal, but can also be plastic.

And the strange thing about the D1 refill is that it comes in two different widths. This means that not all D1 refills fit in all D1 pens. Most Japanese manufacturers use thinner designs, while German manufacturers tend to use thicker ones.

Example of supplement: Schmidt Easyflow 6000,Uni SXR-200,Kaweco soul
Dimensions:Length 67 mm, diameter 2.1 or 2.35 mm

A2 charging

ISO 12757-2-A2, commonly known as the A2 format, consists of a thin metal cylinder with a very thin writing tip. It was mainly used in retractable pens before the 1990s. This filling is rarely seen anymore because it has mostly been replaced by its own filling and plastic parts.

The very thin writing tip is the most important feature here, as pens using A2 will often have a small window for the tip to extend through. This small aperture means that something like the X20 charging won't work.

Example of supplement: Schneider Express 75 M
Glasses:Length 106.8mm, nib 33.4mm from tip of pen, diameter 3.2mm

B3 supplement

B3 is no longer a regular charge, but you may know it because it looks exactly like the charge used in theBic Cristal. This filling is almost always seen in the plastic housing and the plastic cone at the front.

Examples of fillings: Pokka Pen refill, Bic Cristal
Glasses:128mm long (typical, length may vary)

C1 supplement

The C1 or cross cartridge is a screw-in cartridge that is almost always used with swivel retractable pens. The charger (almost always) has a metal housing that is a long, thin cylinder. At the top of the cylinder is a plastic piece that can be screwed into the body of the pen, but which presses against the refill.

The metal barrel is usually replaceable, with the plastic tip being part of the pen. The advantage of this is that the metal component can be taken from a compatible charge that does not use the standard part on top.

This charge is quite similar to the A1, but is held in place by the top instead of the "wings" in the center of the charge.

Example of supplement:Cross Ballpoint charging
Glasses:Length 117 mm, diameter 3.05 mm

G2 supplement

The ISO G2 refill, commonly known as the Parker-style G2 refill, is one of the most common and versatile pen refills ever sold. It is still popular today with pens in all price ranges. This refill size is sometimes known as the "Standard International Ballpoint" refill, but is no more standard than anything else in this section.

The G2 refill was originally used with ballpoint inks, but is designed for hybrid and gel inks. The filling is usually seen in metal, but some manufacturers have also released plastic models.

Example of supplement: Schmidt EasyFlow 9000,Parker QuinkFlow,Itoya quick drying gel
Glasses:Length 98 mm, maximum width 6 mm, maximum width at tip 2.5 mm

X10 charging

The X10 pen cartridge is a variant of the more popular X20 cartridge (explained below), but has a narrower nib. It is also a thin metal cylinder with the same spring stop as the X20. A pen usually uses a metal ring to hold a spring as opposed to pressed "wings".

Examples of pens:Aurora Hastil, Aurora Dissertation
Glasses: 106 mm lang, 3,05 mm diameter

X20 charging

This is another ISO standard filling that is shaped into a long metal cylinder. X20 is very similar to the A2 refill, but is sometimes seen in modern pens. The X20 has a thicker nib than the A2, so the two are not interchangeable. The X20 is usually made of metal, but it doesn't have to be.

It's important to note that the X20 charge can take many forms, some of which are long, thin metal cylinders, while others have a plastic piece on top and are wider in the middle. An example of this is the Schneider Express 740, which is a "jumbo" style X20.

Example of supplement:Schneider Office 765, Schneider Express 740, Schneider Express 775
Example of a pen:Favorite Schneider
Glasses:107mm long, 27mm from tip to center of feather wings

Accessories for roller skates

Rollerball refills are briefly mentioned in the "RB" refill above, noting that the standard length is 110mm and the diameter is 6.3mm. This filling is actually usually followed, but the names vary greatly by company and location.

For example, these refills are often referred to as "European rollerball" refills when they are full size and larger in width, as seen in something likeRotring jazz.

Types of fillings for roller skates

Rollerball accessories may stick loosely to the RB standard, but there is still a great deal of variation from one to the next. In the photo above you can see the Zebra Sarasa gel fill in the "Pilot G2" style next to the Schmidt 8120. The Schmidt 8120 fill is a full size "European" capless roll fill.

You can clearly see that the two are about the same length, but their contours are different. Schmidt has pronounced steps made of black plastic on the top and bottom of the master cylinder. There is also a recessed spring retainer in the plastic base. You can't tell from the picture, but the Schmidt refill is about 6.81mm in diameter, while the Zebra is 6.09mm. This means that the two are not fully compatible.

The filler at the bottom of the picture is the rebranded Schmidt "P" roller filler. This isP8126more specifically, which is a shortened version of the Schmidt 8126 (without the "P"). This cartridge is 97.6mm long compared to the 110mm of the full rollerball cartridge that targets the RB standard set by ISO.

Pilot G2 Charge Vs. Parker-Style G2

Look at this picture:

It is the Zebra Sarasa Clip, which is a Japanese roller ball. Its filling corresponds to the exact dimensions specified in the ISO standard for size RB! Interestingly, Japanese rollerball refills are often referred to as "Pilot G2" sizes or just "G2", due to their immense popularity.Pilot G2 gel olovka. This has caused endless confusion among fountain pen buyers over the years, but it's understandable why: G2 is the ISO standard for a ballpoint pen, but also the name of a mega-popular pen. More people know about the pen than the ISO 12757 standard, so "G2" is often considered a rollerball refill.

That is whypeople examining pencilswill often refer to the ISO standard as "Parker-style G2", while the rollerball size will be referred to as "Pilot G2".

Video with explanation of refilling the pen

And here is a visual explanation of the most popular types of refills.

Proprietary fillings

The topic of proprietary supplements can lead to numerous discussions and articles in itself, but we'll do a brief overview here.

To create a competitive advantage and enable innovative pen designs, many manufacturers have adopted their own customized refill designs. This means that the pen doesn't have to be long and narrow, but it can be short and wide or oddly curved or something in between.

Pilot BRF

A good example of a self-filling pen is the Pilot BRF series. They are similar to Parker-style G2 cartridges, but are shorter and have different contours near the writing tip. This means that some of Pilot's best pens can only use Pilot's own BRFN refills, limiting customers but maintaining Pilot's customer base.

BRF refill is sold as:

BRFN-10with a plastic body, found in pens like Dr. Grip, with Acro ink
BRFN-30which are available in nicer pens, like the Pilot S20, also with Acro ink
BRFwith standard ballpoint ink, with models such asBRF-25-BB

As you can see, correctness allowances add an extra layer of confusion to the market because they do not require any level of standardization and can vary from generation to generation.

Glasses:Length 87 mm, diameter 6.0 mm

Fisher Space Pen RP

One of the most popular and long lasting proprietary refills isFisher Space Pen PR trykrefill. Designed to work in Fisherastronaut pencils, the PR is essentially a shortened, thinned G2 cartridge with a metal body. Using the included plastic converter, the filling can be made to match the G2 standard exactly. Critically, the design of the front of the charge and the shoulder that holds the spring is exactly the same as the G2 specification.

Glasses: 90 mm lang, 4,8 mm diameter