Thule Force 3 XL US Rooftop Cargo Box, 18 cu ft

The Thule Force 3 XL US is a hard-shell rooftop cargo box with 18 cubic feet of listed storage. Its dual-side access and click-indicating mounting system are useful for loading and checking the box, while the listed dimensions and 65-pound weight make roof fit and vehicle load limits important to confirm.

At a glance

Opens from either side of the vehicle for access to cargo.
The mounting system is described as giving a click when the box is safely attached.
SlideLock separates opening and locking functions and indicates when the lid is closed securely.
The manufacturer lists a limited lifetime warranty.

Price

$742.95Save 20%

Reference price: ~~$929.95~~

Price checked: Nov 14, 2026

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Often bought together

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Pros and cons

Pros

Dual-side opening can make it easier to reach cargo from the roadside or curbside.
SlideLock's separate locking and opening functions provide a clear lid-closure indication.
The listed 18 cubic feet offers substantial additional storage for travel gear.

Technical specifications

10 specifications

Identity
Brand	Thule
Model	645850

Storage and construction
Volume	18 cubic feet
Shell type	Hard
Material	Plastic
Color	Black
Water resistance	Water Resistant

Dimensions and installation
Mounting	Roof Mount
Dimensions	89"L x 18"W x 40"H
Weight	65 pounds

What to know before buying

Listing details to confirm

The listed dimensions and 65-pound weight should be considered alongside the vehicle's roof, rack and load limits. Confirm fit and compatible roof bars before purchase. The listing describes the fit as universal but does not establish compatibility with a specific vehicle.

What’s in the box

Included

Rooftop cargo carrier box

Who is it for?

A good fit for

Drivers needing hard-shell rooftop storage for trips or active-use gear.
Buyers who value access to cargo from either side of the vehicle.

Less suited to

Buyers who need a confirmed fit for a specific vehicle without checking rack compatibility.
Anyone who cannot accommodate the listed box dimensions or weight on their roof system.

Thule Force 3 XL US Rooftop Cargo Box, 18 cu ft · photo 2 — Additional product photo 2

Customer reviews on Amazon

4.4 / 5 · 36 ratings

5 stars79%79%
4 stars2%2%
3 stars4%4%
2 stars8%8%
1 star7%7%

Customer feedback highlights ease of installation, perceived quality and storage size, with some buyers describing the size as a good fit without excessive overhang and considering the cost worthwhile. Those impressions may matter to buyers comparing setup and usable roof space, but vehicle-specific fit still depends on the car and rack. The aggregate ratings lean positive, while the lower-star ratings show that experiences are not uniformly favorable.

Positive themes

Customers report that installation is easy.
Customers praise the perceived quality and storage size.
Some buyers consider the cost worthwhile.

Frequently asked questions

How much storage does the Thule Force 3 XL US list?

The listed volume is 18 cubic feet.

Can the box be opened from either side?

Yes. The listing describes access from both sides of the vehicle.

What does SlideLock do?

The listing says it separates locking from opening, automatically locks the lid in place and indicates when the box is closed securely.

What should I check before mounting it?

Confirm that the listed 89"L x 18"W x 40"H dimensions and 65-pound weight work with your vehicle, roof bars and their load limits. The listing does not confirm fit for a particular vehicle.