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Two tritium keychains can look identical in a listing photo and sit at opposite ends of the price range. The visible part, a glowing vial in a metal body, is nearly the same across the market. Much of what decides whether the thing still works in ten years does not show in a photograph at all.
A tritium keychain is a small fob that holds a sealed glass vial of tritium gas, coated inside with a phosphor that glows in the dark without charging.
What is the best housing material for a tritium keychain?
For daily carry, Grade 5 titanium is the housing material to look for: strong, light and corrosion-free. The housing has one job: keep the glass intact through years of being crushed against keys in a pocket. The two ends of a vial are the sealed points, and they break far more easily than the straight body. The failures we see come from clamping the ends during installation, and from drops. Materials differ widely at protecting against that.
Grade 5 titanium (Ti-6Al-4V) is a strong choice for a fob carried every day. It is roughly as strong as many steels at a little over half the weight, it does not corrode, and it will not deform around the vial pocket over time. It also holds a finish well: a bead-blasted or stonewashed titanium body ages into a patina rather than wearing through to bare metal.
Stainless steel is strong and cheap and works perfectly well. The trade is weight. A steel fob is noticeably heavier on a keyring, which can matter on something carried daily.
Aluminum keeps a fob light and easy to machine, and that is the whole case for it. Anodizing can wear through against keys, and the softer body can deform enough around the vial pocket to load the glass. For a decorative item it is fine; for a fob that has to protect a fragile component for a decade, it is the wrong choice.
Brass and copper are chosen for looks and patina, not protection. They are heavy and soft, so buy them because you want the material rather than a rugged marker.
Plastic and resin bodies exist and cost very little. They offer the vial little protection.
What vial size and color should a tritium keychain have?
Buy green in the standard 3x11 mm size if the fob has a job, and any color you like in a large size if it has a look. Size has a large effect on how a fob performs, and it is easy for a listing to leave out. The table covers the tritium vial sizes keychains commonly use, from a small marker dot to the largest vials.
| Size | Role | Trade-off |
|---|---|---|
| 2x6 mm | Marker dot or accent | The first size to become faint with age |
| 3x11 mm | The standard keychain size | Best all-round balance of brightness, cost and housing bulk |
| 3x22.5 mm | The large format, obvious across a dark room | The size to buy if you want the vial to still perform late in its life |
A listing that does not state a size may be implying 3x11 mm without delivering it.
Larger vials read brighter to the eye, and a 3x22.5 mm vial is visibly brighter than a 2x12 mm one. 1.5x6 mm is one of the sizes we use often, alongside 2x12 mm and 3x22.5 mm.
Color is the second lever, and the gap between colors is wide. Green is the brightest color at every vial size, which is why we lead with green. Ice blue is the strong second, while red, orange and purple are substantially dimmer and best chosen for appearance, with a larger vial to compensate. The full ranking and the reasons behind it are in our tritium colors guide.
Can you replace the vial in a tritium keychain?
You can if the housing holds the vial with removable retention, such as a threaded cap or a retaining screw; a glued or potted vial cannot be swapped. A tritium vial glows for up to 25 years. No customer has come back to us reporting a vial going dim. Every vial does dim gradually over that span, though, and at some point you may want a fresh one. Whether that is a short job or the end of the product depends on how the housing retains the vial.
Removable retention, whether a threaded cap, a retaining screw or a slide-in window, makes the vial a consumable and the housing the durable good. One fob can take a new vial more than once and stay on the keys for decades.
Permanent retention, whether glued, potted in resin or press-fit behind a swaged edge, means the fob and the vial fail together. The product has a fixed lifespan whether the machining deserves it or not.
A useful proxy is whether the seller also sells replacement vials. A vendor stocking spares expects you to still own the product in a decade. Our guide to replacing a tritium vial covers what the swap involves.
How can you tell if a tritium keychain uses good vials?
Check whether the listing names the vial manufacturer and states how the vial is distributed, because a buyer cannot inspect phosphor or seal quality. Vials come from a small number of licensed facilities worldwide, and quality differences between them can be real and hard to see. Phosphor grade affects how fast a vial dims beyond the physics-driven decline, and seal quality affects whether it holds its fill at all. A buyer cannot inspect either. We have handled cheaper non-Swiss vials, and the plain difference is that they are not as bright as ours.
That makes provenance one of the few proxies available. A seller who names the vial's origin and states the basis on which it is distributed has a supply chain that can stand the question. Antdesign uses Swiss-manufactured vials, distributed in compliance with US NRC requirements. Our vials are fresh from the Swiss factory, and we sell through them, so there is no ageing stock.
A listing that names nothing leaves that question open. The same logic applies to the housing: "CNC machined titanium" with no grade named is a weaker claim than "Grade 5 titanium," and a seller confident in its parts has every reason to name the grade.
What are the red flags in a cheap tritium keychain listing?
The clearest red flags are missing vial dimensions, photos that are all long exposures, and no named vial source.
- No vial dimensions. A clear warning sign. Size drives brightness and cost, and a seller who leaves it out may not be leaving out good news.
- Only long-exposure photos. Every color looks bright in a long exposure. In strong light you cannot see the glow, although the vial is glowing the whole time. Look for a photo of the colors together, or of the fob in a dark room.
- "Lifetime glow" or a flat "lasts 25 years." The accurate phrasing is up to 25 years, because output declines the whole time.
- No named vial source. Covered above, and worth more than any specification number.
- A price well below the market. The vial is a licensed, specialist component with a real floor cost, and a finished fob priced near a novelty keyring has likely cut corners on the vial, the phosphor or the housing.
- Vague material claims. "Aircraft-grade," "titanium alloy" and "premium metal" are not grades.
- No spare vials offered. It can mean the housing is not serviceable.
Which tritium keychain should you buy?
For one recommendation rather than a framework: a Grade 5 titanium housing with a removable vial, a 3x11 mm green vial from a named manufacturer, from a seller that also stocks spares. That combination handles daily carry, stays findable for many years and can be refreshed rather than replaced.
Adjust from there for taste. A fob that has to be visible across a room wants the 3x22.5 mm vial, and a specific color can be offset by going up a size. For low weight, titanium is already the light option among the metals worth buying.
What to avoid is the cheap middle of the market: an aluminum body, an unspecified vial, and a price that looks like a bargain until the anodizing wears and the glow in the photos turns out to have been a long exposure. To compare housings, vial sizes and colors side by side, the full collection shows the current options, and the standard tritium keychain is the reference build the rest are variations on.
Frequently asked questions
How much should a good tritium keychain cost?
Expect the vial alone to account for a meaningful share of the price, with the rest going to machining and finishing. A well-made titanium fob with a quality vial sits well above novelty pricing, and anything dramatically below that range may have cut something you cannot see.
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Tritium Colors Ranked by Brightness: Green, Ice Blue and Beyond
Replacing a Tritium Vial: When, Why and How