Whether a canister fits your stove comes down to one thing: the valve format on top of the can, not the brand on the label and not the size of the can. Three formats are in circulation — the EN 417 threaded valve, the bayonet latch, and the pierced canister — and a stove is built around exactly one of them, the one its maker specifies. Confirm the format on the canister against the format named in your stove's documentation before you buy fuel. That match is the whole test. Everything else about the can is secondary.
I run that check on a sheet of plywood over two sawhorses in my garage, usually the week before a trip, when the canisters have been sitting in the cold long enough to sting through my fingers. I line them up in a row: the threaded can I use most, a bayonet can that belongs to an old two-burner I keep for car camping, and a pierced canister off a stove I inherited and rarely light. Then I pick each one up and look at the top of it, because the top of the can is the only part that has anything to say.
Pick up the threaded one with me. Turn it over. There is a dimple in the center, a ring of fine machine thread around it, and under that dimple a small spring-loaded valve that sits closed until something pushes it down. Press the tip of a fingernail into the dimple and you can feel it move and come back. That little valve is the reason a can from one company threads onto a stove from another, and it is also the reason people get sloppy: once you have used one threaded can, every threaded can looks interchangeable. They mostly are, at the thread. That is not the same as being interchangeable at the stove.
The threaded valve, and why it made everyone careless
EN 417 is the standard that fixes the thread and the valve on the modern threaded canister. That is the entire practical gift of it. Because the standard pins the geometry, a canister from a brand you have never heard of will screw onto a stove from a brand you have used for twenty years, and the joint will seal, and the stove will burn. This is genuinely good, and it is also how a person ends up at a trailhead holding a can that does not fit: the printed word on the label tells you what is inside the can, not what is on top of it.
The stove side of a threaded connection is a hollow stem inside a collar. Screw the can on and that stem pushes the canister's valve open; unscrew it and the valve closes on its own and the can goes back in your pack. The fit question is whether the stem reaches the valve and whether the two faces meet square with enough thread engaged to hold them there. That is a physical question, and you answer it with your hands, at home, dry, with the stove off.
Bayonet: lugs, not threads
Now the bayonet can. Set it next to the threaded one and the difference is obvious once you know to look — no thread at all, just a collar with three lugs and a notch, and a stove head with a matching receiver and a little lever that clamps down on it. You push and twist a quarter turn and the lever locks it. It is a good system. It is also a completely different latch geometry, and it will not thread onto an EN 417 stove, no matter how confidently someone in a parking lot tells you it will. The two formats were designed to be different so that they could not be confused under pressure.
If you are holding a can with lugs and a stove with a threaded stem, you do not have a fit problem to solve. You have the wrong can.
Pierced: a decision you cannot undo
Third can in the row. This one has no valve you can see or feel. The top is a sealed neck, and the stove that takes it has a spike inside the connector. Screw the can on and the spike lances the seal, and from that moment the can is open. It cannot be reseated. Take it off the stove and what is left in it goes into the room.
That changes the fit question into a commitment question. With threaded and bayonet cans, a mismatch is an annoyance you discover at the bench. With a pierced can, the connection is made once and the can stays on that stove until it is empty. I check those cans twice, because there is no second chance at the answer.
The seal is in the canister, so the canister is the part you inspect
Here is the thing I wish someone had told me early, because it would have saved me an hour of blaming a stove that was fine. The self-sealing mechanism lives in the canister valve, not in the stove. The stove's stem only holds that valve open; it does not make the seal. So when a connection leaks, the usual cause is the can — a valve face with grit or dried mud on it, sand from the bottom of a pack worked into the dimple, an O-ring with a nick in it.
I turn every can over and look at the valve face in good light before it goes in the pack. I wipe it. I do not put a canister back in a pack pocket with loose sand and grit in it, because that is where the damage comes from. If a can's valve looks chewed or dirty in a way I cannot clean off, it does not go on the trip. That is a cheap decision at the bench and an expensive one at camp.
Same valve, different can
The other half of fit is the part nobody photographs. Canister body diameter and height vary between brands even when the valve is identical, and on a direct-mount stove — the kind that screws straight onto the can with no hose — the can body is the base of the whole assembly. A wide, short can puts the burner close to the ground and gives the pot supports a broad footprint. A tall, narrow can raises the burner and puts a wide pot on a small base. Both setups are stable on a flat kitchen counter. Only one of them is stable on the duff beside a tent at dusk with a pot of boiling water on top.
Before a trip I set the pot I actually plan to use on the stove, mounted on the canister I plan to carry, and look at where the pot supports land relative to the pot's rim. If the supports sit inside the rim, the pot can slide. If the base looks narrow relative to the pot, I want to know that at home, not when I am tired. This has nothing to do with which can is better. It is about which combination I am willing to balance a litre of dinner on.
Where I stop, and why
There are adapters that bridge formats, and I am not going to walk you through using one, because I do not use them. An adapter adds a joint between the stove and the can, and every joint in a fuel connection is a place that has to be leak-checked, in a spot where you may not be able to see or reach easily. It also changes how the stove sits — the whole assembly gets taller, and the weight moves up. And a maker's stated compatibility covers the stove as designed, not the stove with something else threaded into it. If the maker says the stove takes one format, the answer is a can in that format.
If your stove shipped with more than one connector in the box, the documentation tells you which one is fitted and which format each takes. Read it rather than assuming. It takes two minutes and it is the only authority that matters here.
The question that settles it
One question, asked before money changes hands or a can goes in the pack: what format does the maker specify for this stove? Not what the photo on the listing looks like. Not what the person at the register thinks. The documentation, or the maker's own specification, because the seal geometry and the valve stem depth are built to one format and not another.
Then do the dry fit at the bench, stove off, valve closed. Thread it on or latch it down and feel for engagement. If it does not want to start, stop. Nothing about a fuel connection gets better with force. I have never once regretted spending five minutes at the plywood bench on a cold afternoon; I have watched a man spend an hour at a trailhead proving why it is worth it.
