Bud Industries
Published on: February 6, 2026 by Josiah Haas
NEMA 4 and NEMA 4X are two of the most commonly specified enclosure ratings, and on the surface, they look nearly identical. They share a lot of common ground, but there’s one critical distinction that can make or break a design in the wrong environment. Let’s break it down.
NEMA 4 is a protection rating established by the National Electrical Manufacturers Association that defines how well an enclosure guards its contents against specific environmental threats. An enclosure carrying a NEMA 4 rating is designed and tested to protect against the ingress of dust, dirt, and other airborne particulates. On the water side, NEMA 4 enclosures withstand splashing water, rain, and even hose-directed water—the kind of repeated washdown you’d encounter on a factory floor. They’re also built to survive the formation of ice on the exterior without sustaining damage.
NEMA 4 enclosures are suitable for both indoor and outdoor use, which is part of why they’re so popular. They’re a workhorse rating: tough enough for demanding environments, versatile enough to cover a wide range of applications. At Bud Industries, NEMA 4 is one of the most frequently specified ratings we see from design engineers, and for good reason.
Here’s the short version: NEMA 4X does everything NEMA 4 does, and then it adds one more layer of protection: corrosion resistance. That single addition is what sets the two ratings apart, and it’s more significant than it might initially sound.
Corrosion is a slow but serious enemy of any metal enclosure. When metals are exposed to moisture, salt, or certain chemicals, a chemical reaction begins to degrade the material. A corroded enclosure loses structural integrity, develops pits and cracks, and eventually fails to keep water and contaminants out, which put the sensitive electronics inside at serious risk.
NEMA 4X enclosures are built from materials that resist this degradation, including stainless steel, polycarbonate or ABS plastic, fiberglass, aluminum, and steel with corrosion-resistant powder coating. The “X” in 4X specifically signals that corrosion protection has been engineered into the design and verified through testing. One example out of many in Bud’s expansive product line is the NF Series fiberglass enclosure. It has both impact strength and high corrosion resistance.
So, both NEMA 4 and NEMA 4X will keep dust and water out. The question is whether your application also needs to stand up to corrosive conditions such as those found in marine environments and chemical plants—and if it does, NEMA 4X is the rating you need.
NEMA 4 is the right call when your application demands solid protection against dust and water, but corrosion isn’t a concern. Think manufacturing plants where enclosures get hit with regular washdowns, outdoor installations where rain and windblown debris are the main threats, or construction sites where ruggedness and reliability matter most.
NEMA 4 enclosures may be more cost-effective than their 4X counterparts because they can be built from a broader range of materials—including options like standard steel that are durable and budget-friendly. In many cases, the cost difference is negligible. In fact, all of Bud’s NEMA 4 enclosures are also rated NEMA 4X. For most applications, the extra protection buys peace of mind.
Not sure which rating fits your project? Bud Industries offers a broad range of NEMA 4/NEMA 4X enclosures in plastic, aluminum, fiberglass, and steel. Browse our full NEMA/IP rated enclosure lineup or watch our video “Tips on Selecting a NEMA 4 Enclosure” to get started.
By the way, many of our plastic, aluminum diecast, and fiberglass NEMA-rated enclosures are included in our industry-leading 5-Day Modifications Program. Fast cutouts plus ample stock at Bud and our distributors means you get your design to market as soon as possible.