Buying Guide: Choosing the Right Gundam Marker for Panel Lining (GM03 and Alternatives)

Panel lining is one of the most satisfying steps in building a Gundam model kit. A few careful strokes can turn a plain plastic surface into a sharp, detailed mecha with depth and realism. But with so many Gundam markers on the market, choosing the right one can feel overwhelming. Should you go for a fine tip or a pour type? Is brown better than gray for white armor? And what about the famous GM03 Brown Liner — is it really the best option?

In this buying guide, we break down the key factors to consider when selecting a panel lining marker, compare the most popular options, and help you decide which one belongs in your tool kit. Whether you're a beginner building your first High Grade or a seasoned collector working on a perfect-grade custom, this guide will point you in the right direction.

Why Panel Lining Markers Matter

Panel lining is the art of applying a thin, dark line into the recessed grooves of a model kit to simulate shadows and mechanical joints. It instantly adds contrast and definition, making even a simple snap-fit build look like a premium display piece. While you can use thinned enamel paints or ink washes, Gundam markers offer a much cleaner, faster, and more beginner-friendly solution. They are essentially felt-tip pens filled with water-based or solvent-based ink that flows into panel lines with minimal mess.

The right marker can make the difference between a crisp, professional finish and a smudged, uneven mess. That's why it's worth understanding the different types before you buy. The most common categories are fine-tip markers (like the GM01–GM05 series), pour-type markers (which have a larger tip and release more ink), and double-ended markers that combine both. Each has its own strengths depending on the kit and your experience level.

• Fine-tip markers are ideal for thin, precise lines on shallow grooves.
• Pour-type markers work best on deep, wide panel lines and can be wiped clean with a finger or eraser.
• Double-ended markers offer versatility, letting you switch between fine and pour tips on the same tool.

GM03 Brown Liner: A Closer Look

The GM03 Brown Liner is one of the most popular Gundam markers among builders, and for good reason. It's a fine-tip marker that delivers a rich, warm brown line that looks especially natural on white, cream, and light gray plastic. Unlike black, which can sometimes appear too harsh or cartoonish, brown provides a softer, more realistic shadow effect. This makes it the go-to choice for many builders working on Real Grade or Master Grade kits where subtlety matters.

When comparing GM03 vs other markers, the key advantage is its balance of color and flow. The ink is neither too watery nor too thick, and it dries quickly without smudging. It also works well with common panel lining cleanup methods, such as a light wipe with a cotton swab or a soft eraser. If you're looking for a reliable, everyday liner for most of your builds, the GM03 Brown Liner is a fantastic starting point. Many builders keep one in their kit at all times.

• Best for: white, cream, light gray, and yellow plastic parts.
• Tip: Use a gentle touch and let the ink flow naturally into the groove — don't drag the tip hard.
• Cleanup: A soft eraser or a slightly damp cotton swab works wonders for removing excess ink.

Alternatives to GM03: Gray, Black, and Pour-Type Markers

While the GM03 Brown Liner is a standout, it's not the only option. For dark-colored plastic — such as navy blue, dark gray, or black — a lighter gray or even a white marker may be more appropriate. The GM01 Gray Liner is a popular choice for dark armor panels, as it creates a subtle highlight rather than a harsh dark line. Meanwhile, the GM02 Black Liner is the classic choice for red, blue, and dark green parts where you want maximum contrast.

Another alternative is the pour-type marker, such as the GM300 series. These markers have a larger, porous tip that releases a controlled flood of ink. You simply touch the tip to the panel line, and capillary action draws the ink along the entire groove. This is much faster than tracing every line by hand, but it requires a bit more cleanup. Pour-type markers are excellent for kits with deep, wide panel lines, such as older Master Grade or Perfect Grade kits. For beginners, starting with a fine-tip marker like the GM03 is usually easier.

• GM01 Gray: best for dark blue, black, and dark gray plastic.
• GM02 Black: best for red, green, yellow, and light blue plastic.
• Pour-type (GM300): best for deep, wide panel lines and large surface areas.

How to Choose the Right Marker for Your Kit

Choosing the best Gundam marker for your build comes down to three factors: the color of the plastic, the depth of the panel lines, and your personal preference for contrast. A good rule of thumb is to use a color that is two to three shades darker than the plastic you're lining. For white armor, brown or gray works beautifully. For red or blue armor, black or dark gray gives a strong, clean look. For dark armor, a light gray or even a white marker can create a striking highlight effect.

If you're just starting out, it's wise to buy a small set of the most common colors: brown, gray, and black. This way, you can experiment on different kits and see which finish you prefer. Many builders find that the GM03 Brown Liner becomes their daily driver, while the black marker is reserved for high-contrast accents. Don't forget to pick up a few extra tips or a cleanup tool like a soft eraser — they make the process much smoother.

• For white plastic: try brown or gray.
• For red/blue plastic: black or dark gray works best.
• For dark plastic: light gray or white for subtle highlights.

Additional Tools to Complement Your Markers

While a good Gundam marker is the star of the show, a few supporting tools can elevate your panel lining game. A soft eraser (like a standard pencil eraser) is excellent for wiping away excess ink without damaging the plastic. Cotton swabs lightly dampened with isopropyl alcohol can also clean up mistakes, especially with water-based markers. For more precise work, a pair of fine tweezers can help hold small parts while you line them.

If you're serious about panel lining, consider adding a bottle of matte varnish to your arsenal. A quick coat of matte varnish after lining seals the ink and gives the entire kit a uniform, non-reflective finish. This is especially important if you plan to apply decals or weathering later. Many builders use the AK11237 Gen-3 Matt Varnish 100 ml for this purpose, as it sprays on smoothly and dries to a beautiful flat finish. It's a small investment that pays off in the final look of your model.

• Soft eraser: quick cleanup without smudging.
• Isopropyl alcohol: removes stubborn ink marks.
• Matte varnish: seals the panel lines and protects the finish.

Choosing the right Gundam marker for panel lining doesn't have to be complicated. Start with a versatile option like the GM03 Brown Liner for most of your builds, and expand your collection with gray and black markers as you tackle different colors and kits. With the right tools and a little practice, you'll be adding professional-grade detail to every model you build. Ready to upgrade your panel lining kit? Check out the AK11237 Gen-3 Matt Varnish 100 ml to seal your work and give your model a flawless finish.