4" Round Electric Box Extender

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Box extensions are one of those items where the UL/code compliance matters more than almost any other specification — you're adding volume to a junction or outlet box and the total cubic inch rating needs to meet NEC requirements for the conductors inside. These 4" round extenders at 16.5 cu. in. each are the right capacity addition for outlets and fixtures that have too many conductors crammed into an existing box.The weatherproof designation makes them appropriate for outdoor outlet boxes and exterior fixture installations where standard extensions would deteriorate. The 4-hole design accommodates the common knockout configurations found in standard round boxes. Gray color is standard electrical gray, consistent with typical outdoor weatherproof installations.Two-pack pricing is practical for anyone doing multiple outlet or fixture upgrades in the same project. Installation is straightforward: secure to the existing box using the appropriate hardware, and your expanded cubic inch rating accommodates additional conductors per NEC fill calculation. If you're not sure whether you need a box extender, a quick fill calculation based on the number and gauge of wires in your box will tell you definitively.

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Used to extend cameras below the eaves of my house. Screwed to mounted junction box just great, nice and tight. Lowered camera and it is mounted securely as well. It came with four plugs which is great to keep crawlies out

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I picked up this 4" Round Electrical Box Extender to add an outlet to a very crowded junction box on my front porch, and it was the perfect solution. Dealing with "buried" or overcrowded boxes is always a headache, but this extender provided the extra depth I needed to tuck in the new wiring without having to tear out the existing box or rework the entire setup.The build quality is excellent—it’s made of heavy-duty, cast-metal that feels like it will easily hold up to outdoor weather. The installation was straightforward, and it created a clean, weather-tight seal that looks professional. If you have an outdoor box that’s running out of space, this is a much more efficient, budget-friendly alternative to a full replacement.

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The extension kits are suited to outdoor / weather and wet location boxes that need additional cubic inches of cavity to conform to cable fill requirements or like needs. These kits are complete extensions, they have a pre-punched gasket to sit between the base box and this extension ring box, two screws to fasten the extension ring to the base box, and four weather tight knockout seals to close up un-used ports. The box is cast metal for durability and tapped screw holding strength and the flange will accomodate both full and fractional round boxes (outdoor style and rated). The knockout ports are trade size 1/2 inch and threaded. They are quick and easy to install with the supplied parts and the foam gasket provides a weather tight seal between the extension and base.

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Not clear from the description but these are 1.5 inches deep.

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We’re upgrading a 1950s house and want Alexa controls throughout it without tearing walls out. So this box extender is a tiny hero — it doesn’t contain the desired Smart relay but it creates the extra space in the electrical box so you can add the (desired) smart relay or module without replacing the box or reworking wiring. It screws in, offers mounting holes for different fixture sizes and wiring layouts, and makes installing that separate relay straightforward and safe. For DIYers or electricians it’s a budget‑friendly, low‑impact solution that avoids a costly box swap. The neutral gray finish is appreciated since it often blends with existing hardware; if it doesn’t, a quick spray paint makes it look like it belongs. Turn power off, fasten the extender, tuck in your chosen relay, and you’ll be linking non‑smart fixtures to an app and using Alexa voice commands like “Alexa, turn off light downstairs” without a full remodel. In our case, we are using this for a particularly tight space, mounting a security camera floodlight right under a roof overhang.

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I installed these Jicoyin 4-inch round electrical box extenders on 2 basement boxes that were used as j-boxes and to hold a simple porcelain light fixture and they worked exactly as intended. The cast construction feels solid and durable, with a quality finish that should hold up well in outdoor environments.The 1/2-inch extension provided the extra depth I needed for wiring connections without having to replace the existing box. Installation was straightforward since the mounting holes aligned properly with my existing box and cover. The gray color matched standard electrical components nicely, giving the finished installation a clean, professional appearance.I also appreciate that these extenders are UL-standard style, which adds confidence when using them in electrical applications. The 16.5 cubic inch volume provides additional space for wire management, making it easier to work within code requirements and reducing crowding inside the box.The package includes two extenders, which offers good value for common lighting or receptacle projects. If you need additional box depth for weatherproof outlets, switches, or light fixtures, these extension rings are a practical and well-made solution.Overall, a quality product that installs easily, fits correctly, and does exactly what it is designed to do.

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First of all, these are not junction boxes per se. These are extensions to round, all weather junction boxes that can increase the volume of the original box to allow for more wiring. When you need these, you really need them because there are code limits to how many wires you should terminate in a box. These seem to be well made and even have a "UL" label.