Pen Refill Codes Explained: G2, D1, C1, X20, A2 and More

Pen refill codes explained with D1, Parker-style G2, C1, X20, A2, and 111 mm refill examples shown side by side — Pen refill codes can help identify common refill families, but length and code alone do not always guarantee compatibility.

Pen refill codes can be confusing because they are not always used the same way across brands, refill standards, retailers, and pen communities. Codes like G2, D1, C1, A2, and X20 can help identify a refill’s general size or shape, but they do not guarantee that a refill will fit your pen.

Some refill codes come from formal refill standards. Others are common industry shorthand. Some are tied to specific brands, and some refill names are simply proprietary model names. That is why two refills can have a similar length but still be completely different in tip shape, shoulder design, rear plug, diameter, or pen compatibility.

If you already know your refill length, you can also compare common sizes using our Pen Refill Finder. If you are new to refill compatibility in general, start with our Pen Refills 101 guide before diving into refill codes like G2, D1, C1, A2, and X20.

Quick Answer: What Do Pen Refill Codes Mean?

Pen refill codes are shorthand labels used to describe common refill families, sizes, and shapes. For example, a D1 refill usually refers to a small 67 mm mini refill, while a Parker-style G2 refill usually refers to a 98 mm refill format used in many ballpoint, gel, hybrid, and pressurized refills.

The tricky part is that refill codes are not always universal. G2 is the best example: a Parker-style G2 refill is not the same thing as a Pilot G2 gel refill. They are different refill families, different lengths, and used in different types of pens.

A refill code can help narrow your search, but you should always check the refill’s length, diameter, tip shape, shoulder, and rear section before buying a replacement.

Find a Refill Code or Length

Looking for a specific code? Jump to:

G2 / Parker-style G2
Pilot G2-style gel
D1 mini
C1 / Cross-style
G1 / A2 / X20
Euro-style rollerball
proprietary refills

Measured your refill already? Jump by size range:

60–76 mm
89–98 mm
102–108 mm
109–115 mm
116–143 mm

Why Pen Refill Codes Are Confusing

Pen refill codes are confusing because they are not one single naming system. A refill name may come from:

A formal refill standard
A brand-specific refill model
A retailer or manufacturer shorthand
A common pen-community nickname
A general size or shape family
A proprietary refill system

For example, D1 is widely understood as a small mini refill format used in many multi pens and compact pens. But G2 can mean either a Parker-style G2 refill or a Pilot G2 gel refill, depending on context.

This is why it is important to treat refill codes as a starting point, not a final answer.

Refill Codes vs Refill Lengths

Refill length is one of the most useful ways to identify a refill, but it is not enough by itself. Many refills are close in length but are not interchangeable.

Pen refill anatomy showing tip, shoulder, body diameter, rear plug, and refill length — Refill compatibility depends on more than length. Tip shape, shoulder position, diameter, and rear design all matter.

A 98 mm Parker-style refill, a 98 mm Montblanc ballpoint refill, and a 98 mm short rollerball refill may all be similar in length, but that does not mean they fit the same pens. The same is true in the 111 mm range, where retractable gel refills, capped rollerball refills, fineliner refills, and proprietary refills can all appear close in length.

When comparing refills, look at:

Overall length
Tip shape
Tip diameter
Shoulder shape
Main body diameter
Rear plug or back end
Spring stop or collar position
Ink type
Pen mechanism

Common Refill Codes Grouped by Length

The chart below groups common refill codes and refill families by typical length. These are practical reference lengths, not a guarantee that every refill in that length range will fit the same pens.

Typical Length	Common Codes / Names	Common Refill Type	Notes
60 mm	Lamy M22	Compact ballpoint refill	A short proprietary Lamy refill used in select compact Lamy pens.
67 mm	D1, D mini, 4C-style mini refills	Mini ballpoint refill	Common in multi pens, compact pens, and small twist pens.
70–76 mm	Short Ohto, Schmidt Mini, Schmidt MegaLine 4876	Compact ballpoint / rollerball-style refills	Often brand-specific; measure carefully before replacing.
89–95 mm	Fisher PR, Zebra F-Refill, Sheaffer K, Zebra JK, Zebra All Metal F-Refill	Compact and brand-specific refills	Similar lengths do not mean shared compatibility.
97–98 mm	Parker-style G2, ISO G2, many Parker-style refills	Ballpoint, gel, hybrid, pressurized, and some rollerball-style refills	One of the most common replacement refill ranges.
102–108 mm	Cross Slim, Lamy M16, Caran d’Ache SwissRide, Schmidt 700, Schneider 75/225/775	Ballpoint and proprietary refills	Many are brand-specific even when close in length.
109–115 mm	Pilot G2-style gel, Euro-style rollerball, Schmidt 888/5888/6040, Lamy M63/M66, Parker Rollerball	Gel, rollerball, fineliner, and proprietary refills	This range contains many lookalike refills that are not interchangeable.
116–143 mm	C1, Cross-style, Ohto 175NP/177NP, Uni-ball Jetstream RT, Pentel Cushion Ball, Zebra PM-701, Pentel R.S.V.P.	Long ballpoint, rollerball, marker, and proprietary refills	Longer refill formats that fall outside the most common compact, Parker-style, D1, and 111 mm refill families.
Varies	Proprietary formats	Brand-specific refill systems	Lamy, Parker, Cross, Sheaffer, Waterman, Montblanc, Fisher, and others may use their own systems.

Common Pen Refill Codes and Typical Lengths

The chart below lists common refill codes, names, and families one by one. Some are formal or semi-standard refill codes, while others are practical refill-family names used by pen buyers.

Code / Name	Typical Length	Common Meaning	Compatibility Notes
D1	About 67 mm	Mini ballpoint refill	Common in multi pens and compact pens. See our D1 Mini Refill Guide for more detail.
D / D mini	About 67 mm	Mini refill category	Often used loosely for D1-style mini refills.
4C-style mini refill	About 67 mm	Japanese-style mini refill family	Often overlaps with D1-style refills, but check the exact refill dimensions.
G2 / ISO G2	About 98 mm	Parker-style G2 refill	Standard Parker-style ballpoint/hybrid/gel-compatible format; not the same as Pilot G2.
Parker-style G2	About 98 mm	Parker-style refill family	Used across many pen brands. See our Parker Style G2 Refill Guide.
Pilot G2-style	About 111 mm	Retractable gel refill family	A brand/family-style term, not the same as ISO/Parker G2.
G1	About 106–107 mm	ISO-style ballpoint refill category	Often discussed with A2 and X20-style refills.
A1	Varies / less commonly referenced	ISO-style ballpoint refill category	Useful in standards discussions but not common in everyday refill shopping.
A2	About 106–107 mm	Standard ballpoint-style refill	Often appears with G1 and X20 in refill identification.
A3	About 106–107 mm / legacy reference	Older or alternate A-style reference	Mention carefully because usage is not always consistent.
B / B1 / B3	Varies / less commonly referenced	ISO-style ballpoint refill categories	Less common in modern consumer searches.
C1	About 116–117 mm	Cross-style ballpoint refill	Often associated with slim Cross-style twist pens.
E	Varies / less commonly referenced	ISO-style ballpoint refill category	Standards-related category, but not a common shopper search term.
F	Varies / less commonly referenced	ISO-style ballpoint refill category	Do not confuse with brand-specific names like Zebra F-Refills.
X10	Varies / less commonly referenced	Large-capacity ballpoint-style refill	Less common than X20 in practical refill searches.
X20	About 106–107 mm	Large-capacity ballpoint-style refill	Common in inexpensive, promotional, and twist-style pens.
Euro-style rollerball / RB	About 110–112 mm	Standard capped rollerball refill family	Often used for capped rollerball pens, but not interchangeable with retractable gel refills.
Schmidt 888 / 5888 style	About 111 mm	Standard rollerball refill family	Usually for capped rollerball pens; length alone does not make it interchangeable with 111 mm gel refills.
Proprietary refill	Varies	Brand-specific refill format	Includes Lamy M16, Lamy M63, Lamy M66, Parker 5th, Fisher PR, and many others.

G2 Refills

The term G2 refill is one of the most confusing refill labels because it can refer to two completely different things.

In most refill-standard and compatibility discussions, G2 usually means the Parker-style G2 refill format. This is a 98 mm refill family used in many ballpoint, gel, hybrid ballpoint, and pressurized refill options.

However, many people also use “G2” to mean the Pilot G2 gel pen refill, which is a longer retractable gel refill around 111 mm. These are not the same refill format.

Parker-style G2 refill compared with Pilot G2 gel refill to show the difference between two commonly confused G2 refill types — Parker-style G2 and Pilot G2 refills are commonly confused, but they are different refill formats.

Parker-Style G2 Refills

A Parker-style G2 refill is usually about 98 mm long and has a distinctive metal or plastic body with a stepped rear section. It is one of the most common refill formats for higher-quality ballpoint pens, rollerball-style ballpoints, hybrid ballpoints, and some gel refill conversions.

Common Parker-style G2 examples include:

For a deeper breakdown, see our Parker Style G2 Refill Guide.

Pilot G2-Style Gel Refills

Pilot G2-style gel refills are usually around 111 mm long and are used in retractable gel pens. They are not the same as Parker-style G2 refills, even though both use the name “G2.”

Common 111 mm gel refill examples include:

For more detail on this size range, see our 111 mm refill guide.

D1 Refills

D1 refills are small mini refills that are usually about 67 mm long. They are commonly used in multi pens, compact pens, small twist pens, and some pocket pens.

Common D1 and D1-style mini refills include:

D1 refills are one of the more consistent refill families, but you should still check the refill tip, ink type, and mechanism compatibility. For more detail, see our D1 Mini Refill Guide.

C1 and Cross-Style Refills

C1 is commonly associated with Cross-style ballpoint refills. These are long, slim refills often used in twist ballpoint pens. In real-world shopping, many people are more likely to search for “Cross refill” than “C1 refill.”

Common Cross-related refill pages include:

Cross ballpoint, Cross Slim, and Cross Selectip refills shown side by side for compatibility comparison — Cross-style refills can look similar by brand name, but Cross Ballpoint, Cross Slim, and Cross Selectip are different refill systems.

Cross compatibility can be especially confusing because Cross-style, Cross Slim, and Cross Selectip refills are not the same thing. If you are replacing a Cross refill, match the specific refill style rather than relying on the Cross name alone.

You can also compare Cross refill families on our Cross Pens Guide.

G1, A2, X20, and 106–107 mm Ballpoint Refills

Some refill codes, including G1, A2, A3, and X20, are often associated with the 106–107 mm ballpoint refill range. These codes are less familiar to many modern pen buyers than D1 or Parker-style G2, but they can still appear in refill-identification discussions.

This length range includes several standard-style and brand-specific ballpoint refills. Examples from this range include:

106 mm and 107 mm ballpoint refills shown side by side, including Lamy M16, Schmidt 700, and Schneider Express refills

This is a good example of why length alone is not enough. A refill may sit in the same general size range as another, but still require a different pen mechanism, shoulder position, or rear-end shape.

Euro-Style Rollerball Refills

Euro-style rollerball refills are often around 110–112 mm long and are commonly used in capped rollerball pens. These refills may be called “standard rollerball” or “Euro rollerball” refills, but compatibility still depends on the pen.

Common examples include:

These should not be confused with 111 mm retractable gel refills such as Pilot G2, Pentel EnerGel, or TUL Gel. The lengths may be close, but capped rollerball refills and retractable gel refills are usually built for different pen mechanisms.

Brand-Specific Refill Codes

Not every refill code comes from a broad standard. Many are brand-specific model names. These can look like codes, but they usually refer to a specific manufacturer’s refill system.

Examples include:

These names are still useful, but they should not be treated the same way as broad formats like D1 or Parker-style G2.

Proprietary Refills

Proprietary refills are brand-specific refills that do not fit cleanly into a common refill-code family. Some proprietary refills are close in length to standard formats, but that does not mean they can be swapped directly.

For example, the Lamy M16 Ballpoint Refill is close to the 106 mm range, but it is still a Lamy-specific refill. The Parker 5th Refill is around 111 mm, but it is not interchangeable with a standard 111 mm gel refill. The Lamy M63 Rollerball Refill and Lamy M66 Rollerball Refill are both Lamy rollerball refills, but they are not the same length or the same refill.

Lamy M16 refill 106 mm ballpoint refill for compatible Lamy pens — Lamy M16 Ballpoint Refill for compatible Lamy ballpoint pens.

Parker 5th Refill 111 mm for Parker 5th Technology pens — Parker 5th Refill, a 111 mm proprietary refill designed exclusively for Parker 5th Technology pens.

Lamy M63 Rollerball Refill 115 mm capped rollerball refill — Lamy M63 Rollerball Refill, a 115 mm proprietary rollerball refill for capped Lamy rollerball pens.

Lamy M66 Refill 110 mm rollerball refill for compatible Lamy capless rollerball pens — Lamy M66 Rollerball Refill for compatible Lamy capless rollerball pens.

When a refill is proprietary, the safest replacement is usually the exact refill model or a replacement specifically designed for that pen.

Refill Examples by Length

The sections below group common refills by length. These are helpful if you have already measured your refill and want to compare possible matches.

60–76 mm Refills

Length	Refill	Type	Notes
60 mm	Lamy M22 Ballpoint Refill	Ballpoint	Short proprietary Lamy refill.
67 mm	Schneider Express 56 D1 Ballpoint Refill	Ballpoint	D1 mini refill example.
67 mm	Lamy M21 Ballpoint Refill	Ballpoint	Short Lamy refill used in select compact pens.
67 mm	Ohto R-4C5NP / R-4C7NP D1 Refill	Ballpoint	D1 / 4C-style mini refill.
67 mm	Schmidt MegaLine 620 D1 Ballpoint Refill	Ballpoint	Pressurized D1 refill option.
67 mm	Schmidt easyFLOW 6000 D1 Refill	Hybrid ballpoint	Smooth-writing D1 refill.
67 mm	Schmidt 635 D1 Ballpoint Refill	Ballpoint	Standard D1 refill example.
70 mm	Ohto 705NP Ballpoint Refill	Ballpoint	Short Ohto refill format.
76 mm	Schmidt MegaLine 4876 Ballpoint Refill	Ballpoint	Short pressurized Schmidt refill.
76 mm	Schmidt Mini 8126 Rollerball Refill	Rollerball	Short rollerball-style refill.

89–98 mm Refills

Length	Refill	Type	Notes
89 mm	Fisher Space Pen PR Series Pressurized Refill	Pressurized ballpoint	Compact pressurized refill.
89 mm	Ohto 895NP / 897NP Ballpoint Refill	Ballpoint	Ohto ballpoint refill family.
89 mm	Schmidt MegaLine 4889 Ballpoint Refill	Pressurized ballpoint	Short pressurized ballpoint refill.
89 mm	Zebra F-Refill Ballpoint	Ballpoint	Common Zebra F-style refill.
95 mm	Sheaffer K Style Ballpoint Refill	Ballpoint	Sheaffer-specific refill style.
95 mm	Zebra All Metal F-Refill	Ballpoint / gel-style family	Longer Zebra F-style refill associated with select Zebra pens.
95 mm	Zebra JK-Refill Gel	Gel	Zebra gel refill format.
97 mm	Caran d’Ache Goliath Ballpoint Refill	Ballpoint	Proprietary Caran d’Ache refill.
97 mm	Fisher Pressurized Universal Refill	Pressurized ballpoint	Fisher universal-style refill.
98 mm	Parker Quinkflow Ballpoint Refill	Ballpoint	Classic Parker-style G2 refill.
98 mm	Parker Gel Refill	Gel	Parker-style gel refill.
98 mm	Schmidt easyFLOW 9000	Hybrid ballpoint	Popular smooth Parker-style refill.
98 mm	Schmidt P900 Ballpoint Refill	Ballpoint	Parker-style G2 refill.
98 mm	Schneider Gelion 39 Gel Refill	Gel	Parker-style gel refill.
98 mm	Schneider Slider 755 Hybrid Ballpoint Refill	Hybrid ballpoint	Parker-style refill.
98 mm	Monteverde Parker Style Ballpoint/Gel Refill	Ballpoint / gel	Parker-style refill family.
98 mm	Ohto G-95NPS Gel Refill	Gel	Ohto 98 mm gel refill.
98 mm	Ohto PG-M05NP Gel Refill	Gel	Ohto 98 mm gel refill.
98 mm	Ohto PG-105NP / PS-107NP Ballpoint Refill	Ballpoint	Ohto 98 mm ballpoint refill.
98 mm	Schmidt P8126 Rollerball Refill	Rollerball	Short capless rollerball-style refill.
98 mm	Zebra K-Refill Ballpoint	Ballpoint	Zebra ballpoint refill format.

102–108 mm Refills

Length	Refill	Type	Notes
102 mm	Cross Slim Ballpoint/Gel Refill	Ballpoint / gel	Cross Slim refill format.
106 mm	Caran d’Ache SwissRide Ballpoint Refill	Ballpoint	Caran d’Ache ballpoint refill.
106 mm	Lamy M16 Ballpoint Refill	Ballpoint	Proprietary Lamy ballpoint refill.
107 mm	Schmidt 700 Ballpoint Refill	Ballpoint	Standard-style ballpoint refill.
107 mm	Schneider Express 75 Ballpoint Refill	Ballpoint	Schneider ballpoint refill.
107 mm	Schneider Express 225 Ballpoint Refill	Ballpoint	Schneider ballpoint refill.
107 mm	Schneider Express 775 Ballpoint Refill	Ballpoint	Schneider ballpoint refill.
108 mm	Sheaffer Classic Rollerball Refill	Rollerball	Sheaffer rollerball refill.

109–115 mm Refills

Length	Refill	Type	Notes
109 mm	Schmidt 8126 Long Rollerball Refill	Rollerball	Longer Schmidt rollerball refill.
110 mm	Lamy M66 Rollerball Refill	Rollerball	Proprietary Lamy refill.
110 mm	Waterman Rollerball Refill	Rollerball	Waterman rollerball refill.
111 mm	Cross Selectip Refill	Ballpoint / rollerball / fiber tip	Cross Selectip refill family.
111 mm	Ohto Ceramic Rollerball Refill	Rollerball	Ohto ceramic rollerball refill.
111 mm	Parker 5th Refill	Proprietary	Parker 5th refill system.
111 mm	Pilot G2 Gel Refill	Gel	Common retractable gel refill.
111 mm	Pentel EnerGel Refill	Gel	Popular retractable gel refill.
111 mm	TUL Gel Refill	Gel	Office-style retractable gel refill.
111 mm	Uniball 207 Gel Refill	Gel	Common 111 mm gel refill.
111 mm	Pilot FriXion Gel Refill	Gel	Erasable gel refill.
111 mm	Uni-ball POWER TANK RT Ballpoint Refill	Ballpoint	Pressurized retractable refill.
111 mm	Schmidt 888 Rollerball Refill	Rollerball	Standard rollerball-style refill.
111 mm	Schmidt 5888 Rollerball Refill	Rollerball	Metal-body rollerball refill.
111 mm	Schmidt 6040 Fineliner Refill	Fineliner	Fineliner refill format.
111 mm	Waterman Ballpoint Refill	Ballpoint	Waterman ballpoint refill.
111 mm	Zebra LV-Refill Gel	Gel	Zebra gel refill.
111 mm	Zebra NC-Refill Gel	Gel	Zebra gel refill.
113 mm	Montblanc Rollerball/Fineliner Refill	Rollerball / fineliner	Montblanc refill format.
114 mm	Montblanc LeGrand Rollerball/Fineliner Refill	Rollerball / fineliner	Montblanc LeGrand refill format.
114 mm	Parker Rollerball Refill	Rollerball	Parker rollerball refill.
115 mm	Lamy M63 Rollerball Refill	Rollerball	Proprietary Lamy rollerball refill.

116–143 mm Refills

Length	Refill	Type	Notes
116 mm	Cross Ballpoint Refill	Ballpoint	Cross-style ballpoint refill.
117 mm	Ohto 175NP / 177NP Ballpoint Refill	Ballpoint	Long Ohto ballpoint refill.
118 mm	Uni-ball Jetstream RT Ballpoint Refill	Ballpoint	Longer retractable ballpoint refill; page coming soon.
121 mm	Pentel Cushion Ball Rollerball Refill	Rollerball	Long rollerball-style refill; page coming soon.
125 mm	Zebra PM-701 Marker Refill	Marker	Longer marker-style refill; page coming soon.
143 mm	Pentel R.S.V.P. Ballpoint Refill	Ballpoint	Extra-long ballpoint refill; page coming soon.

Do Most Refills Fit Into a Code System?

No. Many refills can be described by a code, length, or general shape family, but many others are better identified by brand and model name.

A Parker Quinkflow can be understood as a Parker-style G2 refill. A Schmidt 635 can be understood as a D1 refill. But a Lamy M63, Parker 5th, or Montblanc LeGrand Rollerball/Fineliner Refill is better treated as a specific proprietary refill.

That is why refill identification works best when you combine the code, length, brand, pen model, and physical shape.

How to Identify an Unknown Pen Refill

If you are trying to identify an unknown refill, start with the physical refill rather than the pen brand alone.

Measure the refill from tip to end.
Compare the overall length to common refill families.
Look at the tip shape and shoulder.
Check the rear plug or back end.
Note whether the refill is ballpoint, gel, rollerball, fineliner, or pressurized.
Compare it with a known refill family.
Confirm compatibility before buying.

If you are not sure where to start, use the Pen Refill Finder to compare refill sizes and common replacement options.

Brand Pages for Refill Compatibility

Many refill codes only make sense once you know the brand or pen family involved. These brand guides can help you compare common refill systems:

FAQs

What is a G2 refill?

A G2 refill usually means a Parker-style G2 refill, which is a common 98 mm refill format used in many ballpoint, gel, hybrid, and pressurized refills. However, G2 can also refer to the Pilot G2 gel refill, which is a different 111 mm refill family.

Is Parker-style G2 the same as Pilot G2?

No. Parker-style G2 and Pilot G2 are different refill formats. Parker-style G2 refills are usually about 98 mm long, while Pilot G2-style gel refills are usually about 111 mm long.

What is a D1 refill?

A D1 refill is a mini refill, usually about 67 mm long, commonly used in multi pens, compact pens, and small twist pens.

What is a C1 refill?

A C1 refill is commonly associated with Cross-style ballpoint refills. In everyday shopping, many people are more likely to search for Cross ballpoint refills than C1 refills.

What is an X20 refill?

An X20 refill is generally associated with a large-capacity ballpoint-style refill around the 106–107 mm range, often found in inexpensive, promotional, or twist-style pens.

Do refill codes guarantee compatibility?

No. Refill codes can help narrow your search, but they do not guarantee compatibility. Always compare length, diameter, tip shape, shoulder, rear plug, and pen mechanism.

Why do some refills not have a code?

Some refills are proprietary, which means they are made for a specific brand or pen model rather than a broad standard. Examples include Lamy M16, Lamy M63, Lamy M66, Parker 5th, Fisher PR, and many Montblanc, Cross, Sheaffer, and Waterman refills.

Final Takeaway

Pen refill codes are useful, but they are not a complete compatibility system. Codes like D1, G2, C1, A2, and X20 can help identify a refill family, but the actual fit still depends on the refill’s length, diameter, tip, shoulder, rear design, and pen mechanism.

The safest way to choose a replacement is to compare the refill you already have against a known refill family, then confirm the specific refill page or brand guide before buying.