Which coupler fits which beer?

Why the question is harder than it sounds

A publican takes delivery of a keg his coupler will not accept. He searches online for a “brewery → spear type” list, finds several – and they contradict each other. That is no accident.

We have collected more than a thousand assignments from thirteen countries and learned in the process that the widely circulated lists share one problem: almost all of them are copies of one another. Identical order, identical typos, in some cases brands that are not even traded in the country concerned. Anyone who finds two such lists that agree does not have two pieces of evidence, but one.

The most common short circuit runs: “they belong to the same group, so the same connection.” We worked this through for a Polish group that owns four well-known brands.

Four brands, one owner, two spear types. Anyone reasoning from the group gets it wrong in half the cases here. The same picture in Belgium: one brewing group runs one of its brands on flat (A-type), two others on EU Sankey (S-type).

The reason is historical. Spears belong to the keg stock, not to the brand. When a brewery is taken over, its fleet moves with it – and that fleet is not converted just because the name on the building changes.

For Germany – the largest draught beer market in Europe – there are the fewest entries. Not because there are no sources, but for the opposite reason:

For practical purposes that says something useful: the rule of thumb “flat unless something says otherwise” holds up better for German stock than anywhere else. It is just hard to document – because silence is not evidence.

The Czech Republic is the reverse: there, two independent specialist sources each list around a hundred breweries by coupler type and agree on every name we checked. It is the only national list that passes that test. By number the flat spear (A-type) leads there, by volume the EU Sankey spear (S-type) – the major brands of one group are on EU Sankey (S-type) without exception.

One attribution persists stubbornly and we were unable to confirm it: “type G, so the United Kingdom.” We have now documented the triangular spear (G-type) in the United Kingdom, in Austria at two operations, in the Baltic states – a German specialist dealer explicitly sells the three-lobe coupler (G-type) as matched to an Estonian brewery – and in Germany exactly once, at a Thuringian brewery.

So there is no clean country assignment.

Technically it is a special case anyway: type A and type G are identical inside. The same valve, the same down tube, the same spare parts – only the body is three-lobed on the outside instead of flat. Couplers are therefore not interchangeable, wear parts are. That is a workshop observation of our own, not a standard.

When the keg is standing in front of you, you do not need a list. You need a caliper.

This is what a spear looks like from the inside – five types, taken apart:

Exploded views: Aobaosi Spears.

• Measure the body diameter. The quickest and most reliable difference – and not something the naked eye can estimate reliably.
• Look at the outer shape. Round and flat: type A. Round, sitting inside the neck: type S. Three-lobed: type G. Combined with a bayonet lock: type M.
• Do not go by the thread. The neck is the same on all common types: 2 inches, 14 threads per inch. It tells you nothing at all – and that is also why a keg can be converted.

The US Sankey (D-type) special case. There is no body figure for type D, and that is down to the design.The other types have a body that sits on the neck – which is why they all measure more than the thread. On the US Sankey (D-type) the body sits inside the neck and finishes flush with it.

It comes in two versions: with a standard thread of 2 inches × 14 threads per inch – fits any normal European neck – or threadless, in which case the body is recessed into a threadless neck and held by a retaining ring. It is held there by retaining lugs that grip into the neck – not a collar resting on top, but a lock that disappears into the neck. According to the manufacturer's drawing the part measures 53.7 mm across the retaining lugs, the inserted body 50.2 mm and the upper opening for the coupler 38.9 mm. The threadless design comes mainly from the British and American markets.

Both are around fifty millimetres – the thread at 2 inches nominal is 50.8, the threadless body 50.2. It is the same size, just held in two different ways: once by the thread, once by the retaining ring. That is why the US Sankey (D-type) does not belong in the same row as the 74.5, 70 and 68 millimetre bodies – those measure a part above the neck, and the US Sankey (D-type) has none.

For practical work that has a consequence which can get expensive: a keg with a threadless neck will not take a standard spear, of any type. Anyone taking on such kegs needs a neck conversion to a standard thread first – that is work on the keg, not a parts swap.

Out of that comes the rule that is faster than the caliper: you recognise a US Sankey (D-type) by the fact that there is nothing to measure. Where a body stands above the neck, it is not one. And the second question is then not “how big”, but “threaded or not”.

The 74.5 millimetre problem: flat spear (A-type) and combi spear (M-type) share the same body dimension. Measure alone and you have two candidates. They are separated by the view from above: on the combi spear (M-type), below the CO₂ valve of the seal sits a ball-shaped stainless steel counterpart, clearly recessed. On the flat spear (A-type), the end face of the down tube lies almost flush in the seal, level with the spear head – a flat view with no recessed ball. The caliper narrows it down, the decision is made inside the spear.

Two features that are faster than the caliper

The lug marking. On the EU Sankey spear (S-type) the retaining variant is marked on the lug: no mark means the older version without a retaining hook, III or R means a hook is present but not fixed to the body, S means the hook is welded on. The variants need different seals – miss that and you order the wrong set. The same system exists for the flat (A-type) and the combi spear (M-type).

Count the turns. The standard thread of 2 inches and 14 threads per inch needs around ten turns before the spear is seated. A coarse thread – as found on kegs from the eighties and especially on polyurethane-clad designs – is tight after three to five. That works without tools.

If the keg is not yet in front of you, our compatibility matrix will help. It holds more than a thousand entries from thirteen countries – and, which matters to us more than the number, the strength of evidence for each entry.

Of the entries in our matrix, only a good tenth are documented in the strict sense – that is, supported by at least one source that is not a copy of another. Just under a third are plausible, nearly half are thin, four entries are contradictory.

We show that rating on every single entry instead of hiding it. We never communicate an entry rated “thin” as a commitment. That is uncomfortable, but it is the only way of handling this data that we can defend.

If you can close one of these gaps – because you know the spear of one of these breweries yourself – write to us. We correct the matrix continuously, and we note when a figure came from outside.

In brief

There is no reliable “brewery → spear” assignment, because the spear is tied not to the brand but to the individual keg – and kegs move between container sizes, countries, varieties and owners.

What is reliable: first the look at the neck, then the caliper. If a body sits on the neck, 74.5 millimetres means flat or combi (M-type) and 70 millimetres means triangular (G-type). If the body sits inside the thread, it is a EU Sankey (S-type) or a US Sankey spear (D-type). Between flat (A-type) and combi (M-type), the recessed stainless steel ball under the seal decides. Everything else is probability, ours included.