Short answer
Uni Paint markers are oil-based, valve-action paint markers. The PX-21 has a 1.2 mm fine line, the PX-20 a 1.8 to 2.2 mm medium bullet and the PX-30 an 8 mm broad line, per the listings. The PX-20 listing describes opaque, glossy marks on metal, glass, wood, rubber, concrete and plastic that withstand weather, heat and abrasion. For art on paper and rocks, Uni’s water-based Posca is the better fit.
Uni Paint marker sizes
Uni Paint PX-21, PX-20 and PX-30 compared
| Model | Line | Tip | Best for |
|---|---|---|---|
| PX-21 | Fine, 1.2 mm | Fine bullet | Labels, small parts, writing on glass |
| PX-20 | Medium, 1.8 to 2.2 mm | Medium bullet | Everyday marking on metal, plastic, rubber, concrete |
| PX-30 | Broad, 8 mm | Broad | Lumber, crates, steel, large marks |
Line widths are from the Amazon listing titles. On Amazon, the PX-20 is sold in two-packs of single colors and in an assorted six-pack; the PX-30 in two-packs of black, white, yellow, red, blue, gold and silver.
Uni paint marker PX-20
The PX-20 is the classic medium. Its listing describes permanent medium bullet-tip markers that make clear, bold paint marks on light and dark surfaces; opaque and glossy marks on virtually any surface, naming metal, glass, wood, rubber, concrete and plastic; valve action for smooth flowing paint with good coverage; and fast-drying oil-based paint that withstands extreme weather, heat and abrasion without fading. It also notes that the paint contains a solvent that lets it bond to clean surfaces, and suggests lighter colors for dark surfaces and darker colors for light ones. The assorted six-pack has black, blue, green, yellow, red and white.
Uni paint marker PX-21
The PX-21 is the fine 1.2 mm version. It is the one for writing: serial numbers, small labels, names on glass and fine detail. Fine tips run out of paint at the tip faster, so re-prime more often by pressing the tip down on scrap.
Uni paint marker PX-30
The PX-30 is the broad 8 mm marker for big marks: lumber grades, crate numbers, steel cut lines and outdoor equipment. Yellow and white are the high-visibility choices on dark materials. Other wide markers, including water-based ones for posters, are on thick paint markers.
How to start a Uni Paint marker
- Shake
With the cap on, shake until the mixing ball moves freely, then keep shaking a few seconds more.
- Pump the valve
On scrap material, press the tip down a few times until paint flows into the tip. Do not prime on the item.
- Write steadily
Use light, even pressure. If the line fades, shake and press again rather than pushing harder.
- Dry and cap
Let marks dry before handling, and cap the marker tightly.
Clean surfaces first: oil and dust are the main reason marks fail. Use oil-based markers in a ventilated room, since they give off solvent fumes as they dry.
Uni Paint versus Posca and Sharpie
Uni Paint compared with Posca and Sharpie
| Marker | Paint | Best for | Removal |
|---|---|---|---|
| Uni Paint PX series | Oil-based | Metal, glass, plastic, outdoor marking | Needs a solvent once dry |
| Posca | Water-based pigment | Paper, rocks, wood, canvas, fabric | Wipes off smooth surfaces |
| Sharpie oil-based | Oil-based | Similar jobs to Uni Paint; extra fine to medium | Needs a solvent once dry |
Posca is also a Uni product; Amazon listings for Posca name Uni and Mitsubishi Pencil. The two lines suit different jobs: Posca for art, Uni Paint for marking. For the whole category, see oil based paint markers; for specific surfaces, paint markers for metal and paint pens for plastic.
Colors
Uni Paint PX-20 listings on Amazon include black, white, red, yellow, blue, light blue, green, orange, violet, gold and silver. Color-specific guides: yellow paint markers, blue paint markers, orange paint markers and red paint markers.
Uni Paint markers on Amazon
Every size, PX-21, PX-20 and PX-30, each listing checked by hand.
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Uni Paint PX-20 paint markers, medium, assorted 6 pack
Black, blue, green, yellow, red and white in the medium PX-20, per the listing.
- 1.8 to 2.2 mm
- 6 colors
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Uni Paint PX-20 oil-based paint markers, medium, black 2 count
Two medium blacks for marking light materials.
- 1.8 to 2.2 mm
- Black
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Uni Paint PX-20 oil-based paint markers, medium, white 2 count
Two medium whites for dark metal, rubber and plastic.
- 1.8 to 2.2 mm
- White
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Uni Paint PX-21 oil-based paint markers, fine 1.2 mm, white 2 count
The fine PX-21 in white for labels and writing.
- 1.2 mm
- White
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Uni Paint PX-30 oil-based paint markers, broad 8 mm, black 2 count
The broad PX-30 for lumber, crates and large marks.
- 8 mm
- Black
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Uni-Paint PX-30 oil-based paint marker, broad tip, white
A single broad white PX-30 for high-visibility marks on dark materials.
- Broad tip
- White
Each pick links to an Amazon listing we checked by hand. Prices, colors and pack sizes change on Amazon, so check the listing before you buy. As an Amazon Associate we earn from qualifying purchases.
Questions people ask
What are the best paint marker pens?
It depends on the job. For art on paper, rocks, wood and canvas, Posca scored highest overall among pump-action acrylic markers in Sarah Renae Clark’s 2026 comparison. For marking metal, glass, plastic and outdoor items, oil-based markers such as Uni Paint PX-20 and Sharpie oil-based are the usual choices, because solvent-based paint grips slick surfaces and resists weather.
Will paint markers stay on metal?
Oil-based paint markers do, on clean metal. The Uni Paint PX-20 listing says the paint contains a solvent that lets it bond to clean surfaces and withstands extreme weather, heat and abrasion. Water-based acrylic paint markers can be scratched off bare metal unless sealed. Degrease the metal with rubbing alcohol first for the best grip.
What’s the difference between paint pens and markers?
A paint pen holds opaque paint, water-based acrylic or oil-based, that sits on top of the surface and covers it, so light colors show on dark materials. A regular marker holds ink, usually dye, that soaks in and stays translucent. Uni Paint is a paint pen; a classic permanent marker is ink.
Are Uni Posca markers erasable?
On smooth surfaces, yes. Posca, which is made by the same Uni company family as Uni Paint, says its water-based paint is permanent on porous surfaces and erasable on smooth surfaces such as glass, where a damp rag removes mistakes. Uni Paint, being oil-based, is much harder to remove from smooth surfaces once dry.
Is Uni paint marker waterproof?
Uni describes Uni Paint as oil-based paint that withstands extreme weather, heat and abrasion without fading, which in practice means it resists water once dry on clean surfaces. Let marks dry fully before exposing them to rain or washing. Nothing is permanent on every surface, so test on your material.
Sources
Last reviewed 2026-10-12. Specs and availability change; check the listing before you buy.