FIVKLEMNZ Rooftop Cargo Bag Review: Big Space, Small Fuss

A rugged 21 cu ft rooftop cargo bag that’s truly waterproof, fits cars with or without racks, and offers huge storage for road trips on a budget.

Price: $79.99

Original Price: $109.99

Rating: 4.3/5 (8592 reviews)

Pros

Cons

Rolling into a rainy New England weekend with four people, a dog, and camping gear is usually an exercise in Tetris. With the FIVKLEMNZ 21 cu ft rooftop cargo carrier, we ended up with something rarer: empty floor space and no duffel bags wedged between kids’ feet.

This soft-sided roof bag isn’t trying to compete with premium hard-shell boxes from Thule or Yakima. It’s aimed at families and road‑trippers who want a lot more space, don’t want to install a full rack system, and don’t want to spend $500+ to get it. After several trips in different weather and on different vehicles, we found it delivers on those core promises—with a few caveats you should understand before you trust it with your only suitcase.

First impressions and what you’re actually getting

Out of the storage bag, the FIVKLEMNZ feels more serious than the typical budget rooftop cargo carrier. The 840D PVC fabric is thick and rubbery, more like a commercial dry bag than a cheap nylon duffel. Our gear editor described it as “closer to a river raft than a tote bag”—that’s a good thing for waterproofing.

Inside the kit, you get:

The zipper and flap system is where we usually see budget carriers cut corners. On this one, the zipper is chunky and rubber-coated, with a wide storm flap that overlaps the teeth. The flap uses hook-and-loop segments (think Velcro-style) to stay down. It’s not refined, but it feels purpose-built.

If you’re used to sleek, molded cargo boxes, this will look like a giant black brick on the roof. It’s not pretty, but the shape is practical for cramming in soft bags, tents, and pillows.

Fitting 21 cubic feet of real-world gear

On paper, 21 cubic feet is abstract. In practice, here’s what we fit for one family camping trip on a Subaru Outback with factory crossbars:

We still had room to stuff in jackets and a folded soft cooler around the edges. The flexible walls make it easy to pack odd shapes compared to a rigid box.

For a second test, one of our reviewers used it on a Honda Civic with no roof rack, relying solely on the included door hooks and anti‑slip mat. Packed with two large duffels, a stroller frame, and a pack‑and‑play, it sat a bit wider than the roof, but still within the mirror width. If you have a truly small car, a 21 cu ft bag will look comically oversized and might introduce more wind noise than you’re comfortable with. For compact sedans, we’d lean toward a 15 cu ft bag unless you absolutely need the capacity.

Mounting with and without a roof rack

We mounted the FIVKLEMNZ four different ways:

1. On crossbars and side rails (Subaru Outback) 2. Between side rails only (Toyota RAV4) 3. On a bare roof with door hooks (Honda Civic) 4. On a pickup cab roof with a short rack (Toyota Tacoma double cab)

On vehicles with rails or crossbars, the process is straightforward: lay down the anti-slip mat, center the bag, route the straps under or around the bars, and cinch them tight. It took about 10–12 minutes the first time, and under 5 minutes once we knew where each strap should go.

Without a roof rack, the process is more nerve‑wracking the first time, mainly because you’re trusting strap hooks anchored in the door jambs. Once we placed the anti-slip mat and routed the door hooks, closing the doors over the straps gave us a surprisingly solid mount. We drove a 120‑mile highway loop at 65–80 mph and didn’t see the bag shift more than a couple of millimeters on the mat.

Our staffer who owns a Thule Pulse roof box pointed out the trade‑off: installation here is slower and more hands‑on, but you don’t need to buy or permanently mount crossbars. If you’re going to use a cargo solution once or twice a year, that’s a big advantage.

A quick comparison snapshot

Below is how the FIVKLEMNZ stacks up against two popular alternatives we’ve tested:

The RoofPax is the closest apples‑to‑apples comparison: it’s more expensive but has slightly cleaner hardware and labeling. The Thule box is in a completely different category; it’s better in nearly every practical way except cost and capacity per dollar.

Waterproofing where it matters: hours in the rain

Waterproof claims on rooftop cargo carriers are often optimistic. We tested this bag three different ways:

In the first two scenarios, the contents were bone‑dry—no damp corners, no wicking at the seams. That’s better than we usually see from budget carriers; the high‑frequency welded seams and thick PVC do their job.

During the hose test, we deliberately aimed water directly against the zipper from close range. After 10 minutes, we found a light misting along the inside of the zipper flap and very slight dampness on a towel placed directly under the zipper path. Not soaked, not dripping, but enough that we wouldn’t put laptops or paper documents up there without additional dry bags.

In other words: for real‑world road rain, snow, and spray, this behaves like a truly waterproof rooftop cargo carrier. For abuse testing that exceeds normal driving conditions, the weak point is still the zipper line—as with almost every soft carrier.

Stability, wind noise, and the highway test

On the road, we look for three things with rooftop cargo bags:

1. Lateral movement and wobble 2. Strap loosening over time 3. Added noise and drag

At 70–75 mph on I‑95, with the bag fully loaded and mounted on crossbars, movement was minimal. We stopped after the first 30 minutes to recheck and found one strap had loosened slightly—about half an inch of slack. After re‑cinching all straps firmly, they stayed tight for the next three hours.

On the Civic (no rack, door hooks only), we were more cautious. Our tester checked straps every 45 minutes on the first trip. There was some very minor fore‑aft rocking visible in the rearview mirror when hitting expansion joints, but the anti‑slip mat kept the base planted. Again, no meaningful shifting over a 120‑mile loop.

Noise is where a hard aerodynamic box still wins. On the Outback, we noticed a low whoosh above 60 mph—more of a broad whoosh than a whistle. With the Civic, the extra frontal area and less streamlined roof made that whoosh more apparent. It’s not deafening, but if you do multi‑state drives weekly, a more aerodynamic, molded solution will feel more refined.

From a fuel efficiency standpoint, our long‑term Outback tester logged a 1.5–2.0 mpg drop compared to the same route without the bag, which is in line with what we see from other large rooftop carriers.

Usability details: zippers, straps, and living with it

Day‑to‑day usability is where cheap carriers usually undermine themselves. The FIVKLEMNZ avoids most of the obvious pitfalls but still has some budget DNA.

The included luggage lock is more of a token accessory than real security. It keeps the zipper pulls together but won’t slow down anyone determined. Like all soft carriers, this is a weather and space solution, not serious theft protection.

Durability after multiple trips

We put roughly 1,200 miles on this carrier over the course of testing—two multi‑day trips and several shorter runs. After that, here’s what we saw:

Our automotive editor, who has seen cheaper 500D‑600D fabric carriers fail after a single season, was impressed by the material choice at this price. The thicker fabric not only improves waterproofing but also resists abrasion from grit and roof racks.

That said, this is still a soft bag with external straps. You’ll want to:

Treated reasonably, we expect this to last several years of occasional use. If you’re a weekly ski warrior or a contractor hauling gear constantly, you’ll outgrow a soft bag like this and should be looking at a heavy‑duty hard box or basket.

Who gets the most out of this carrier

During testing, it became clear who this rooftop cargo bag really serves well:

If you’re deeply concerned about theft, are bothered by wind noise, or you routinely carry fragile valuables, a hard cargo box like the Thule Pulse or Yakima SkyBox is a better (but far more expensive) choice. If you only need a bit of extra space for occasional IKEA runs, this 21 cu ft size is probably overkill; a smaller 15 cu ft bag will be easier to live with.

For its $79.99 price point, though, the FIVKLEMNZ nails the fundamentals: it’s genuinely waterproof in real weather, carries a ton of gear, works on vehicles with or without racks, and feels more robust than most budget rooftop cargo carriers we’ve tested. As long as you’re willing to spend a few extra minutes on careful installation and you keep realistic expectations about security and noise, it’s a smart, high‑value upgrade for your next long drive.

View on Amazon