Yaocom 12 Pcs Knockout Seal Electrical Box 1 Inch Knockout Plugs Round Steel Removable Seal Cap for Closure Unused Box Outlets, Compatible with Size of The Conduit Pipe

A simple fix that disappears once installed

A good knockout plug should be almost forgettable: it goes in easily, sits flush, and stays put. That’s exactly the experience I had with the Yaocom 1-inch knockout plugs. I used them to close unused conduit knockouts in a few metal junction boxes and a surface-mount panel cover during a cleanup and labeling day in the shop. The short version: they fit correctly, feel sturdier than their price suggests, and remove without a fight when you need the hole back.

What you’re getting

This is a 12-pack of 1-inch trade-size knockout seals—stamped steel caps with springy retention tabs that snap into standard 1-inch conduit knockouts in metal boxes and enclosures. The finish on mine is a light gray/silvery plating that looks at home next to galvanized boxes and painted enclosures alike. There’s no gasket and no promises of a weatherproof seal; these are for blocking dust and debris and for closing unused holes to tidy up an installation.

Each cap is a single piece—no screws, no multi-part hardware. That’s a plus for speed work and for situations where you’ll be popping them in and out during a remodel.

Build quality and finish

Out of the pack, the plugs feel solid. The stamping is consistent, edges are deburred well enough that I wasn’t worried about slicing a glove or catching a conductor as I maneuvered them into place. The retention ears have a good amount of spring without feeling flimsy. I’ve used bargain-bin KO plugs that deform if you look at them wrong; these hold their shape and still flex as needed to bite the knockout.

The plating is even, with no flakes or rough spots on the ones I used. They’re not showpieces, but they present cleanly and don’t scream aftermarket patch. Once seated, they sit low and look like they belong.

Fit and compatibility

The key detail with any knockout plug is sizing. “1 inch” refers to trade size, not the literal hole diameter. In practical terms, that’s the standard 1-inch conduit knockout you’d find in typical steel boxes, panel covers, and enclosures. These plugs matched that spec correctly in all the gear I tried, including:

• Newer commercial junction boxes with relatively thin walls
• Older, thicker panel blanks where some cheaper plugs tend to pop out
• A painted steel equipment enclosure with slightly out-of-round knockouts

In thin-gauge metal, the snap-in force is mild but positive; in heavier-gauge or slightly distorted knockouts, I needed a firmer thumb press, but the plug still seated without tools. Depth-wise, the spring ears have enough reach to accommodate the common range of enclosure thicknesses. If you’re working with unusually thick or layered steel (e.g., a retrofit ring plus the enclosure), you may need a two-piece screw-type seal instead—but that’s an edge case.

A quick note on material: these are designed for metal boxes. You can physically snap them into some plastic enclosures, but retention in plastic varies wildly and isn’t something I rely on.

Installation and removal

Installation is straightforward:

1. De-energize and verify the area is safe to work in.
2. Clear any burrs from the knockout.
3. Angle one edge of the plug into the opening, then press firmly on the opposite side until it snaps home.

On a couple of tight, painted knockouts, I gave the plug a very slight hand-bend across its diameter before starting the first edge; that preload made the snap easier without deforming the face. If you’re wearing gloves, you can also squeeze the retention ears slightly with needle-nose pliers as you start the first edge, but I rarely found that necessary.

Removal is just as painless. A small flat-blade screwdriver slipped under the lip will leverage the first edge out; a wiggle and it’s free. If you can access the backside, a gentle push on one ear helps. I’ve had no issues with plugs getting mangled during removal, which is useful if you’re using them as temporary closures during a rough-in phase.

In use: sealing and safety

Once installed, these plugs do exactly what they should: block the opening, keep debris and critters out, and restore the enclosure’s barrier to finger contact. They’re not watertight, and they’re not intended to maintain a NEMA rating or provide an airtight seal. For wet locations or washdown areas, look to a listed weatherproof closure with a gasket.

Indoors, they’ve been perfectly adequate in dusty utility spaces. I’ve also used a couple in non-electrical metal projects to clean up stray holes—purely cosmetic—and they blended in nicely.

If you’re working under inspection, remember that unused openings must be effectively closed. I didn’t find a UL mark on the plugs I used, so if your authority having jurisdiction is strict about listings, confirm acceptability before using them on inspected commercial work. For general maintenance and residential projects where a specific listing isn’t required by the inspector, they’re a practical solution.

Durability and corrosion resistance

Over a few months, the plugs I installed have held tight with no loosening. The spring in the ears hasn’t relaxed, and there’s no visible corrosion indoors. The plating should fend off normal humidity, but I wouldn’t count on it for coastal or corrosive environments. If you need long-term outdoor resistance, go with stainless or a properly rated closure.

Because the face sits low and edges are smooth, conductors sliding by don’t snag. That sounds minor until you’ve fought a cable past a sharp-edged patch—no such drama here.

Little details that matter

• Low-profile look: They don’t protrude, so they won’t interfere with surface-mount conduit runs routed close to the box face.
• No special tools: Fingers and a small screwdriver are all you need.
• Reusability: They tolerate a few cycles of in/out without losing tension, which makes them handy during phased work.
• Quantity: A dozen in the pack is the right number for day-to-day shop use—enough to cover a small job and still leave spares in the van.

Limitations and gotchas

• Size-specific: This is a 1-inch-only pack. If your work spans multiple trade sizes, you’ll still need a mixed kit.
• Not weatherproof: No gasket, no NEMA rating—don’t use these to seal outdoor boxes where water intrusion is a concern.
• Listing: I didn’t see a UL or other listing mark. That won’t matter everywhere, but it can matter in commercial or inspected installations. Check local requirements.

Who these are for

If you do residential or light commercial electrical work, or you maintain facilities with a mix of older boxes, these 1-inch KO plugs are the kind of consumable that saves time. They’re also great to keep on hand for temporary closures during a project or to clean up an enclosure you’re repurposing. For heavy industrial, harsh environments, or highly scrutinized projects, you’ll want a listed and possibly gasketed closure, and potentially stainless hardware.

Bottom line

The Yaocom 1-inch knockout plugs are exactly what I want from a simple hardware item: correct sizing, solid spring tension, clean finish, and no surprises during install or removal. They sit flush, they stay put, and they’re priced so you can keep a pack in the truck without thinking twice.

Recommendation: I recommend these for indoor use in standard metal electrical boxes and enclosures, especially for maintenance, remodels, and general shop work where a quick, reliable closure is needed. They’re durable, easy to use, and the 12-pack is practical. If you need a weather-rated or listed solution for an inspected job, verify local requirements or step up to a gasketed, listed knockout seal. For everything else, these get the job done and then disappear—just like a good knockout plug should.