KK magsun 4 Packs Octagon Electrical Box Cover, Galvanized Steel Metal Junction Box Covers, Blank Flat Outlet Box Cover for 4 inch Octagonal Box

I spent a weekend tidying up some legacy wiring in a basement and garage, and a four-pack of KK magsun octagon box covers turned out to be the kind of small hardware that makes the job feel complete. These are blank, galvanized steel plates meant to cap 4-inch octagonal electrical boxes—common for ceiling light locations that have been converted into junctions. They don’t try to be anything fancy; they just aim to sit flat, cover safely, and stay put.

Build and finish

Out of the package, the covers look and feel like mid‑gauge, galvanized steel. They’re not so thick that they feel overbuilt, but they’re not flimsy either. If you press firmly at the center, there’s a hint of flex, which is typical of flat steel blanks in this category; once installed with two screws, that flex disappears and the plate sits taut against the box without “oil‑canning.”

The edges on my set were generally polished and comfortable to handle. One cover had a tiny burr on a corner that I knocked down with a couple of strokes from a file—nothing dramatic, but worth mentioning if you plan to install them barehanded. The finish is on the shinier side for galvanized steel. That makes them look fresh and clean against a new box, but it also means they stand out a bit more against the dull gray of older boxes. If you want them to blend in, a quick scuff and a coat of primer/paint matches them to typical box finishes.

I encountered a very light protective oil film on two of the four covers—again, not unusual with stamped steel parts. A wipe with a rag and household degreaser took care of it in seconds. After a few weeks in a slightly damp basement environment, they’ve shown no signs of rusting or discoloration.

Fit and compatibility

The plates measure about 3.75 x 3.75 inches, sized for standard 4-inch octagon boxes. Screw slots lined up perfectly with every box I tried—both new work and older boxes already in place. The covers sit flush and square on the raised rim of the box, with enough play in the slots to compensate for boxes that aren’t perfectly plumb.

A few boundaries to keep in mind:

• These are for octagon boxes, not 4-inch square boxes or round pancake boxes.
• They’re blank covers—no knockout, switch, or receptacle openings—so they’re only for sealing junctions.
• They’re not gasketed or rated for wet locations. For outdoor or damp-rated enclosures, use a cover designed for that purpose.
• They’re not a structural support. Don’t hang fixtures or fans from a covered junction box.

And remember the obvious but important code note: if you’re using these to cover a junction, that box must remain accessible; don’t bury them behind drywall or insulation.

Installation

Installation is simple: two screws and you’re done. The covers don’t ship with fasteners, which is normal for this category but easy to forget in the moment. Plan on using standard 8‑32 machine screws sized to your box depth and any mud rings—1/2 inch works for most plain boxes; 3/4 inch gives a little extra reach when you’re dealing with thicker plaster or shallow mud rings. If your box is painted or the threads are gummed up, chase them with an 8‑32 tap or a sacrificial screw first to avoid cross‑threading.

The polished edges do make them more comfortable to handle than generic stamped covers, but I still wear gloves when working around old boxes with sharp knockouts. Each cover took me under a minute to align and tighten. With the screws snugged down evenly, the plates sit flat without any rattling or gaps at the corners.

A few small tips:

• If a box lip is bent or dinged, true it up with pliers before installation so the plate seals evenly.
• To quiet any vibration on thin wall boxes, a thin foam gasket or a dab of painter’s caulk at two corners can help—though I didn’t need either here.
• If you plan to paint, scuff the galvanized finish with a Scotch‑Brite pad, wipe with mineral spirits, prime, and topcoat. Paint adheres well with that prep.

Everyday performance

Covers like these don’t have a lot to “perform,” but two things matter: they should protect wiring from accidental contact and they should stay put over time. Installed over a handful of junctions, these haven’t loosened, bowed, or buzzed, even where there’s occasional vibration from a nearby garage door opener. The slots have enough metal around them to resist deforming if someone gets heavy‑handed with a screwdriver. I’ve bumped a ladder against one and it didn’t dent.

The bright galvanized finish has stayed clean and hasn’t picked up surface rust in a basement with fluctuating humidity. If you’re installing in a coastal environment or truly damp space, paint will add another layer of protection, but for typical indoor utility areas, the raw finish is holding up fine.

How they compare

Compared to bargain-bin blanks I’ve used, these feel a notch sturdier and, importantly, they arrive flatter and more consistent. I didn’t have to hunt for two covers that weren’t warped to make a pair look right on the same wall—a small but real frustration with cheaper plates. Against premium, heavy-gauge covers, the KK magsun plates are lighter and less industrial. If you’re covering boxes in a high‑abuse environment (think a commercial shop with carts banging into walls), you might prefer thicker, painted steel. For residential basements, garages, and utility rooms, this gauge is appropriate.

One area where I’d like to see improvement is the inclusion of hardware. A small bag of 8‑32 screws would make these more turnkey, especially for DIYers who assume covers come with fasteners. It’s also worth noting the finish choice: galvanized is practical, but if you want a muted gray to match conduit and boxes, some competitors offer factory‑painted options. That’s easy to fix with a rattle can, but it’s still an extra step.

Quality control and consistency

Across the four-pack I tested, three covers were essentially flawless; one had that small burr and a minor scuff. In use, neither issue mattered, but it suggests there’s a little variability at the factory level. The slots were cleanly punched, edges mostly dressed, and all plates were flat out of the box. Packaging protected them well enough; I’d rather wipe off a light oil film than receive rusty steel.

Who these covers are for

• Homeowners cleaning up legacy junctions in basements, attics, and garages
• Pros who want a reliable stock of blank octagon covers for standard service calls
• Anyone consolidating or relocating light fixtures and converting old boxes into junctions

If you’re working in finished spaces where appearance matters, plan to paint them to match wall or ceiling color. If you need weatherproofing or a specific color/texture out of the box, look for a different cover style.

The bottom line

The KK magsun octagon box covers do the boring job you buy them for: they fit, they sit flat, and they keep fingers and debris out of live wiring. The galvanized steel is appropriately rigid, the edges are mostly well finished, and installation takes seconds—just remember you’ll need your own 8‑32 screws. The shiny finish won’t be everyone’s favorite, and a lone burr in my set hints at occasional QC hiccups, but those are minor marks against an otherwise dependable piece of hardware.

Recommendation: I recommend these covers for indoor residential and light commercial use. They offer a solid balance of fit, durability, and ease of installation at a fair per‑cover cost. If you want a muted or color‑matched look, plan to paint them; if you need weatherproofing or heavy‑duty thickness, choose a different cover style. For everyday junction box closures, these are an easy win.