Yakima SkyBox NX 18 Rooftop Cargo Box

The SkyBox NX 18, which Yakima also lists as the SkyBox NX XL (part 8007370), is for the household that needs the full 18 cu ft a ski week or a family camping trip takes, wants to open the box from whichever side is away from traffic, and would rather not pay for the Thule Motion 3 XL's glossy finish and one-hand lid. It is the best overall pick on our rooftop cargo box list because it gets the fit questions right: skis to 195 cm, a 24 to 40 in crossbar spread, a flat floor and a lifetime warranty on a box built in the USA.

Skip it if your garage door is the constraint (the shell is 16.5 in tall before the rack) or if you open the box several times a day and want the slickest latch on the market.

Capacity is the headline, and the floor is what makes it usable. Yakima states 18 cu ft in a shell of 84 x 36 x 16.5 in with an unobstructed flat floor; Rack Warehouse lists the usable interior at 77 x 27.5 in. BetterTrail explains why the floor is flat: the mounting clamps sit low and barely protrude into the cargo area, where the Thule's hardware pushes up into the load space. OutdoorGearLab singles out the same flush floor, with none of the ridges and gaps its testers found in competing boxes. In BetterTrail's loading test the box took three pairs of adult skis with poles alongside two pairs of children's skis.

Fit is the second strength. The instruction sheet gives a 24 to 40 in crossbar spread, the widest among our picks, and the clamps take Yakima StreamLine bars as well as factory, aero, round and square bars. The hardware is tightened with a torque wrench that clicks three times when the clamp is tight enough, then comes out so it does not take up interior space; OutdoorGearLab also noted an audible click when the box seats on the bars.

The lid opens from either side, with SKS lock cores and a full-metal handle, and there are tie-down points molded into the interior. The NX nano-texture on lid and base is the practical alternative to glossy paint: BetterTrail and OutdoorGearLab both flagged scuffing on the glossy Thule and INNO boxes, and OutdoorGearLab prefers the Yakima's matte look because it hides dirt and marks.

The independent verdicts line up. BetterTrail named it Best Overall Roof Box in its August 2026 roundup, OutdoorGearLab scored it 76 out of 100 (third of eight, behind the Thule Motion 3 XL at 80 and the INNO Wedge 660 at 77), and Switchback Travel calls it a close second to its top pick and the cheaper option among the premium 18 cu ft boxes.

The lid does not open as far. BetterTrail measured 12 in of opening height against 14 in on the Thule Motion 3 XL and 14.5 in on the Thule Force 3 XL. Two inches matters when you are sliding a cooler under the lid from the side of a tall SUV. OutdoorGearLab nonetheless counts the opening as wide, so read this as a comparison with Thule rather than a flaw on its own.

The latch takes more effort than the sliding latches on Thule's Force 3 and Motion 3, per BetterTrail, and OutdoorGearLab found the handle's closed indicator not quite as foolproof as Thule's. Switchback Travel mentions owner reports of lock durability problems, which we could not verify further. The separate torque wrench is the other recurring complaint: both reviewers point out it is easy to lose, and without it you cannot torque the clamps to spec.

Noise is average for the size; Switchback Travel lists road noise compared with sleeker designs as the box's main weakness, and OutdoorGearLab calls it bulky with a less premium feel than the Thule. Weight is 53 lb on Yakima's product page and 52 lb on its instruction sheet (about 51 lb on reviewers' scales), a two-person lift onto a tall roof. The load limit is 165 lb, but Yakima's sheet is explicit that the vehicle's roof rating governs if it is lower, recommends staying under 80 mph with the box fitted, and says to re-check the hardware after a short drive.

Against the Thule Motion 3 XL: same 18 cu ft, dual-side access, 165 lb limit, lifetime warranty and US manufacture. The Thule has the taller opening, a one-hand lid, PowerClick mounts with a built-in torque indicator and 200 cm ski length, in a higher price class with a glossy finish that scuffs. The Yakima has the wider crossbar spread, the scratch-hiding texture and the flatter floor.

Against the INNO Wedge 660: the INNO is 5.5 in shorter and fits most garages, but it holds 11 cu ft and skis to about 182 cm. If your garage door clears 16.5 in plus your rack, the Yakima's extra 7 cu ft is worth more than the INNO's sleeker profile.

Against the SportRack Vista XL: the SportRack matches the 18 cu ft on paper, but it is 63 in long, opens only from the rear, mounts with U-bolts through holes in the floor and is rated for 100 lb. It suits occasional trips; the Yakima is the box you leave on all season.

The SkyBox NX 18 is the sensible 18 cu ft box: dual-side opening, real ski length, the widest crossbar range and a lifetime warranty, in a finish that keeps looking new. You give up two inches of lid opening and a slicker latch compared with the Thule Motion 3 XL, and the torque wrench needs a permanent home in your glovebox. For most families that is the right trade.