$14.99 CAD
Screws onto the collar of the Antminer S19 / S21 threaded-collar shroud and closes the 6-inch port when the duct is off. Seals an idle machine in seconds, comes off just as fast, and keeps a shared duct trunk honest. PETG, made to order in Montreal, Quebec.
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This threaded duct cap screws straight onto the collar of the Antminer S19 / S21 Threaded-Collar Shroud — Dual 120 mm to 6″ and closes the 6-inch port when the duct comes off. A machine that is out of service goes from an open hole in your wall run to a sealed face in about two seconds, and back again just as fast when it is time to hash.
It exists because an uncapped shroud on an idle machine is a leak in the building. Cold outside air walks back down the duct all winter, the room heats less evenly, and dust drifts in through a 6-inch opening pointed straight at the hashboards you just cleaned.
On a shared duct trunk it is worse than a leak. An open collar on a stopped machine is the lowest-resistance path in the whole run, so the machines that are actually working push part of their air backwards through it instead of out of the building. Capping the idle ones puts the flow back where it belongs.
The coarse thread on D-Central’s threaded-collar shroud, and only that. It is a companion part cut to that collar, not a generic 6-inch duct plug: the plain, venturi, offset, clamp-groove and bayonet collars all terminate differently and none of them take a screw cap.
The cap sits in a 167.1 × 167.1 × 17.4 mm footprint, so it clears a rack neighbour and a wall run without fouling either.
If the shroud on your machine is a bayonet or clamp-groove version, keep them ducted or blank them at the duct end instead — see the Antminer S19 / S21 Bayonet-Lock Shroud and the Antminer S19 / S21 Clamp-Groove Shroud for how those collars terminate.
Everybody improvises this first: a plastic bag and an elastic, a square of stiff card taped over the collar, a rag stuffed in the opening. All three work until the day they do not. A bag gets pulled loose, tape lets go in the heat around a rack, and a rag is the one thing you never want near a fan inlet on a machine that somebody else might switch on.
A threaded cap engages the same collar the duct uses, so it seats on a surface designed to seal and stays there under vibration. It is one continuous piece of PETG with the thread formed as part of the body — no gasket to perish, nothing to unglue, and it lives in a toolbox for years without deforming.
| Fits | The threaded collar on the Antminer S19 / S21 threaded-collar dual 120 mm to 6″ shroud |
|---|---|
| Intake | Threaded 6″ collar |
| Outlet | Sealed — blanking cap |
| Footprint | 167.1 × 167.1 × 17.4 mm |
| Material | PETG |
| Colour | Black or orange PETG |
| Construction | Single continuous body — no assembly, no fasteners, no glued joints |
| Design files | Open source, CC BY-SA 4.0 — free to download, use, modify and redistribute |
| Download | threaded collar cap bundle (ZIP) — STL, CC BY-SA 4.0 licence, installation and safety guide |
| SKU | DC-ACC-CAP-D120-6 |
This cap and the collar it screws onto were drawn together by D-Central Technologies — our thread, our geometry, open-sourced by us — and both are released under CC BY-SA 4.0 at the 3D models download center, this one at the threaded collar cap entry. Thread profile included, free to print, modify and sell. A companion part is exactly the kind of thing an owner should be able to make more of at three in the morning without asking anyone’s permission.
The file sits one click away in the threaded collar cap bundle: STL, CC BY-SA 4.0 licence, and the installation and safety guide.
Ordering it here gets a finished one in PETG, black or orange, made to order and shipped from Montreal, Quebec, which is usually the sensible call for a part this small. Publishing the thread costs us nothing we want back — a sale here, or a gift at D-Central’s fund page, is what keeps the drawing board busy on the next companion part.
Collars, receivers, couplers and ports are all sized to each other in the D-Central shroud and ducting system.
The Antminer S19 / S21 Threaded-Collar Shroud — Dual 120 mm to 6″. It is cut to that collar’s thread. The plain, venturi, offset, clamp-groove and bayonet shrouds in the same family end in different collar geometry and a screw cap has nothing to bite on.
No. Never close the exhaust of a powered machine. The heat has nowhere to go, the fans work against a dead end, and the miner will be into thermal protection long before you notice. Power down, let the fans stop, then cap.
Two reasons, and the second one costs money. A capped machine keeps outside air and dust out of your room and your hashboards. On a shared duct trunk it also stops the idle unit acting as a free vent for the machines that are running, which quietly steals flow from the ones earning.
It seats on the same thread the duct uses, so it seals against a surface built for it, and it does not fall off, blow away or get pulled toward a fan when somebody powers the machine up without checking. It also survives a toolbox and a Quebec winter, which is more than tape manages.
Yes — that is one of its better uses. Capped collars keep packing debris and workshop dust out of a machine in transit or on a shelf. Pair it with the Antminer S19 / S21 Dual 120 mm Intake Filter Ring on the front and both faces of a stored machine are closed off.
| Weight | 100 g |
|---|---|
| Dimensions | 16.71 × 16.71 × 1.74 cm |
| Colour | Black, Orange |
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Last reviewed August 19, 2026.
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