FIVKLEMNZ 21 Cubic Car Rooftop Cargo Carrier Roof Bag Waterproof for All Top of Vehicle with/Without Rack Includes Topper Anti-Slip Mat + Reinforced Straps + 6 Door Hooks + Luggage Lock

What it is and who it’s for

The FIVKLEMNZ roof bag is a 21-cubic-foot soft rooftop cargo carrier designed to add serious storage capacity to cars, crossovers, and SUVs—with or without factory roof racks. If you need more room for luggage, camping gear, or seasonal cargo without investing in a hard-shell box and crossbars, this bag is a compelling, budget-friendly alternative.

I used it across two trips: one on a compact hatchback with no roof rails and one on a three-row SUV with crossbars. In both cases, it turned cramped packing into a workable, organized setup, and it did so without drama once properly installed.

Setup and fit

Installation is straightforward, but attention to detail pays off. The bag ships with 10 reinforced straps, six door hooks for vehicles without rails, an anti-slip mat, and a basic luggage lock. On the SUV, I anchored to the crossbars and side rails; on the hatchback, I used the door hooks under the weatherstripping. Both methods worked, though anchoring to rails is predictably cleaner and faster.

A few notes from use:
- Clean the roof first. Dust under the mat reduces grip and can scuff paint.
- Place the bag so the zipper faces the rear. This matters for wind and water resistance.
- Pre-route and snug the front straps before the rear; it stops the bag from creeping back under airflow.
- Tie off the strap tails to prevent flapping. A simple roll-and-tuck or a small Velcro strap fixes most noise.

The anti-slip mat helps keep the bag planted, especially on smoother roof surfaces. On one windy highway segment, I found it started to shift slightly; trimming the mat so it didn’t protrude beyond the bag and re-tensioning the straps solved it. If your roof is particularly slick, painter’s tape at the leading edge can keep the mat from lifting.

One manufacturer note bears repeating: don’t attach the front and rear straps to just the side bars. Anchor to crossbars or use the door hooks. Side-load on side rails can stress the straps and fabric over time.

Capacity and real-world packing

At 52 x 40 x 18 inches, the bag is legitimately roomy. I fit a mix of four carry-on rollers, two medium duffels, a compact tent, and soft goods stuffed around gaps. On the SUV, I pushed volume further with two large suitcases and still had space for camp pillows and odds and ends. The flexible sides let you shape the load, which is a real advantage over hard boxes for awkward items.

A few packing tips:
- Put hard-sided items at the base to create a flat platform, then soft bags on top and sides to fill voids.
- Keep moisture/temperature-sensitive items (electronics, food, medications) inside the cabin.
- Don’t overload height; if you can’t easily roll and seal the zipper flap, rework the load.

On-road performance

Stability was better than expected for a soft bag. Properly tensioned, it didn’t sway or “pump” at highway speeds on either vehicle. I did a quick stop after the first 10–15 minutes each time to recheck strap tension—the load settles as air flows—and that eliminated the minor slack that can creep in early.

Noise was minimal once the strap tails were secured. I noticed a faint hum on the hatchback at 70+ mph until I shortened and tucked the tails; after that, wind noise blended into normal road sound.

Fuel economy took a modest hit, as it does with most roof cargo. On the SUV, I saw roughly one extra partial fill over a day’s driving. The compact car saw a smaller but noticeable decrease. Aerodynamics are not the bag’s strong suit; if efficiency is paramount, a low-profile hard box will perform better.

Materials and weatherproofing

The bag is made from 700D PVC with heat-welded seams and a double-layered waterproof cover. The zipper is protected by a wide Velcro-sealed storm flap. When I did my part—packing below the seam line, fully closing the zipper, and smoothing the flap—everything inside stayed dry through hours of steady rain and intermittent spray. After a slushy, salt-spray drive, the exterior was crusted but the interior gear was dry and clean.

Important nuance: this is a soft carrier. Extreme weather, long-term abrasion, or improper strap routing can compromise waterproofing. If you expect days of heavy winter mix or keep the bag up for weeks at a time, consider adding an internal dry bag or packing sensitive items in individual dry sacks. Also beware of overstuffing; if the zipper is under strain, water resistance drops.

The 700D fabric feels robust and resisted scuffing from strap hardware. In freezing temperatures, the material stiffens a bit, which can make opening the corners slightly harder, but it softens quickly once handled.

Mounting without roof rails

Using the door hooks is entirely workable if you take care with placement. I slid each hook under the weatherstripping at the door frame, then firmly reseated the rubber so it formed a proper seal. No leaks in the cabin once the stripping was pressed back in. If your door gasket feels loose, spend the extra minute to massage it flush; that step is worth it.

I doubled up front anchoring (two hooks per side) on the hatchback to counter airflow, then used one or two per side at the rear depending on load. The bag stayed centered and didn’t migrate. If you park outside, crack the doors to release strap tension before a cold snap to avoid compressing the gasket too tightly overnight.

Day-to-day usability

• Loading/unloading: The wide opening and long zipper make top-loading easy. I appreciated the flexibility to shape around oddly sized gear.
• Security: The included lock is basic. It’s fine as a zipper keeper to prevent accidental opening; for theft deterrence, I’d add a small cable lock around a rail if you have one.
• Storage: The bag folds down neatly. Getting it back into the carry pouch takes a tidy fold; a slightly roomier pouch would make life easier, but it’s manageable in a few minutes.
• Cleaning: Expect bug splatter on the leading edge after highway runs. Warm water and a soft sponge did the job. Avoid harsh solvents; they can degrade the PVC coating.

Limitations and caveats

• Not as aerodynamic or quiet as a low-profile hard box.
• Soft bags inherently rely on correct setup for weather resistance; sloppy zipper/flap closure is the main failure mode.
• The anti-slip mat can shift if it catches wind—trim and position it carefully, and recheck tension after your first highway miles.
• Plan your strap routing. Avoid routing that drags across sharp edges or exhaust heat.

Who will like it, and who won’t

You’ll likely appreciate this bag if:
- You need big seasonal or trip-only capacity but don’t want permanent racks.
- You drive different vehicles and want a carrier that adapts to both.
- You pack bulky but not fragile items: luggage, tents, sleeping bags, coats, beach chairs.

You may want something else if:
- You drive long distances in extreme weather frequently and want set-and-forget waterproofing.
- You prioritize fuel efficiency and low wind noise above all else.
- You’re carrying delicate or high-value items that require hard-shell protection.

Practical tips from use

• Put the zipper to the rear and fasten the full storm flap every time.
• Snug straps in a front-to-back sequence, then recheck after 10–15 minutes at speed.
• Tie off strap tails; even small flaps create noise and can loosen knots.
• Use the lock to keep the zipper pulls together and tucked under the flap.
• Don’t attach front/back straps to side rails alone; use crossbars or door hooks as intended.
• Consider packing sensitive items in dry sacks during heavy-weather seasons.

Recommendation

I recommend the FIVKLEMNZ roof bag for drivers who need a large, flexible, and affordable way to add cargo space a few times a year or for road trips. It’s easy to mount on vehicles with or without roof racks, swallows a surprising amount of gear, and—when installed correctly—stays secure and dry through typical rain and highway speeds. It won’t match a hard-shell box for aerodynamics or set-and-forget waterproofing in extreme conditions, and it benefits from careful loading and strap management. But for the price, portability, and capacity, it’s a highly practical upgrade that meaningfully improves comfort and space on the road.