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Tonneau Cover Comparison: UnderCover Ultra Flex Vs. BAKFlip MX4

Updated on Nov 13, 2025

Out of all tonneau cover styles, hard-folding is undoubtedly the most popular. Boasting impressive security features, ultra-low-profile styling, and effortless operation, these tonneau covers are a must-have addition to any truck, so long as your wallet can afford them.

Of the hard-folding tonneau covers sold on RealTruck, two of the top options include the BAKFlip MX4—RealTruck’s best-selling truck bed cover—and the UnderCover Ultra Flex—a similarly-priced offering from RealTruck brand, UnderCover.

In this feature, we’re pinning these two tonneau covers against each other to determine which design best suits your needs. Stay tuned as we compare all the features buyers care about most, including material, installation difficulty, price, and warranty.

Table of Contents:

Construction

Style and Design

Operation

Price and Warranty

Which Tonneau Cover is Right for You?

At a Glance

If you don’t have time to read through this whole comparison, check out the chart below for a quick feature breakdown of the two tonneau covers.

Tonneau Cover	UnderCover Ultra Flex	BAKFlip MX4
Panel Material	Double-thick aluminum-skinned	High-density polymer-reinforced aluminum
Design	Hard tri-fold	Hard tri-fold
Profile (Protrusion Above Bed Rail)	Flush	Flush
Latch Mechanism	Automatic slam latches	Re-engineered automatic latching panels
Installation	Click-in clamp system	All-new click-in installation
Warranty	5-year warranty	5-year warranty
Price (July 2025)	Starting at $1,149.00	Starting at $1,149.00

As you can see, both tonneau covers are very similar on paper, down to the identical starting price point. To gauge the minute differences, we’ll have to dig deeper into both tonneau covers.

Build Quality: Materials and Construction

First, let’s talk about build quality. Both tonneau covers feature primarily alloy construction, including aluminum frames and aluminum-skinned top panels. However, the BAKFlip MX4 takes the slight edge in the durability department thanks to the recent release of the product’s third generation, which makes notable improvements in build quality.

Some of the Gen 3 BAKFlip MX4’s standout upgrades include heavy-duty polymer-reinforced top panels, re-engineered latch components, and beefier corner caps. These upgrades are specifically designed to enhance strength, security, and durability, making the BAKFlip MX4—RealTruck’s best-selling truck bed cover—better than ever.

One area where the MX4 falls short of the Ultra Flex is the finished interior surface. While the MX4 is unfinished, UnderCover treats every Ultra Flex to a plush carpeted liner for a premium look and feel.

Design: Aesthetics and Profile

Frankly, neither. Both brands do an excellent job of producing a sleek, minimalistic, low-profile tonneau cover that blends effortlessly into the bed. Both feature sleek, matte-black finishes that resist corrosion, further enhancing their stealthy appearance.

The only standout difference between the two covers is their corner cap designs, with the BAKFlip MX4 featuring smooth, rounded corner caps that finish off the side rails, compared to the Ultra Flex’s flush-cut side rails. While durability may be slightly improved with the Ultra Flex, the BAKFlip is ever so slightly more aesthetically pleasing.

Operation: Installation and Usability

With both tonneau covers’ design and build quality being so similar, surely the operation of each cover will differ, right?

To further emphasize the similarity between these bed covers, there’s very little difference in the way both covers are installed and operated. Both the MX4 and the Ultra Flex utilize RealTruck’s new click-in mounting system, comprising clamp-on side rails with a click-in cover. This design makes solo installations easier than ever, with both being easily accomplishable in around 30 minutes, requiring little to no modifications.

Operation-wise, the covers are also similar. With the updated versions of each cover, both feature a single pull cable to release each side latch, freeing the cover to fold forward toward the bulkhead. Once folded forward to expose ⅔ of the bed, you can either secure the covers using the integrated straps or fold them once more against the cab, securing them upright with integrated prop rods for complete bed access.

Warranty and Support

Lastly, let’s consider arguably the most important factor of each bed cover—warranty and support. Once again, both covers are backed by the same 5-year warranty. Additionally, both truck bed covers are RealTruck products, meaning each is covered by our industry-leading customer service.

Once again, the BAKFlip MX4 and UnderCover Ultra Flex tie.

Which Tonneau Cover Comes Out on Top?

So, which tonneau cover is superior?

This has been one of our closest product battles to date. Similar build quality, features, operation, and identical warranties make both the BAKFlip MX4 and UnderCover Ultra Flex exceptional selections. However, if there can only be one victor, we’ll have to give it to RealTruck’s best-selling BAKFlip MX4—after all, there’s a reason this bed cover continuously outsells all other truck bed covers on the market.

The BAKFlip MX4 boasts exceptional security, unparalleled build quality, sleek styling, and hassle-free installation and operation—all in a package that’s ever so slightly lower profile and more polished than the Ultra Flex.