Truck toolbox sizing by bed width and rail span
A crossover toolbox rests on both bed rails, so the rail-to-rail span decides whether it fits. None of the bed tables on this site list that span. Weather Guard's full-size boxes are 72.0 inches across the bed and its extra wide box is 27.5 inches front to back. Better Built lists 63.0 inches for mid-size and 69.0 for full-size. Weather Guard's fit guide says to measure the vehicle.
Which width matters
A bed has three widths. The width between wheel wells is the narrowest and limits sheet goods. The inside width is taken at the floor. The rail-to-rail span is taken across the top of the bed sides, and it is the one a crossover box spans. The vehicle table fields wheel_well_width_in and inside_width_in are not the rail span, and the table does not list that span. Use them to rule a box out, not to rule it in. The bed measuring guide covers the tape method.
Sizes makers publish
Weather Guard's spec guide GM8061 (dated 04/24) labels length as the long side of the box, which lies across the bed, and width as the short side. It also lists Better Built boxes. All figures are in inches.
| Maker and style | Length | Width | Height | Trucks listed |
|---|---|---|---|---|
| Weather Guard full-size standard saddle, 127-0-04 | 72.0 | 20.0 | 18.0 | Silverado, Ram, F Series, Sierra, Titan, Tundra |
| Weather Guard full-size low profile, 121-52-04 | 72.0 | 20.0 | 18.0 | Same list; Ram marked as not Classic |
| Weather Guard full-size extra wide, 117-0-04 | 72.0 | 27.5 | 18.5 | Same list |
| Weather Guard full-size lo-side, 174-0-04 | 56.0 | 17.0 | 13.0 | Same list |
| Better Built mid-size low profile, 79211104 | 63.0 | 20.0 | 14.0 | Colorado, Ranger, Canyon, Tacoma |
| Better Built full-size low profile, 79011003 | 69.0 | 20.0 | 14.0 | Silverado, Ram, F Series, Sierra, Titan |
| Better Built full-size standard, 79011012 | 69.0 | 20.0 | 13.0 | Same list |
| Better Built chest, 79011017 | 48.0 | 17.5 | 18.0 | Silverado, Ram, F Series, Sierra, Titan, Tundra |
The guide lists the standard full-size saddle at 75.0 lbs and the extra wide at 97.0 lbs, empty. Add that to your payload math.
How makers say which beds
Weather Guard's 2025 truck box fit guide is a grid of box models against truck, with bed columns such as 5.5 ft, 6.5 ft and 8 ft. Its notes: the guide applies to 2018 or newer model years, the buyer should measure the vehicle, one mark reads "Does not fit Ram Classic or 2018 & older models," and another reads "Does not fit 2024 or newer Ford Ranger models." The GM8061 truck rack row adds that it does not fit the Toyota Tacoma. The fit chart guide explains those marks.
Bed widths on file
| Truck | Between wheel wells | Inside width | Maker source |
|---|---|---|---|
| Ford F-150 2021 to present | 50.6 | not published | Ford 2026 F-150 specifications |
| Ford Super Duty 2023 to present | 50.5 | 66.9, Ford's width at floor (maximum) | Ford 2025 Super Duty specifications |
| Chevrolet Silverado 1500 2019 to present | 50.63 | 71.4 | Chevrolet 2026 configurator |
| Chevrolet Colorado 2023 to present | 45.5 | 58.8 (GMC Canyon page: 58.1) | Chevrolet 2026 compare page |
| Toyota Tacoma 2024 to present | 44.7 | not at floor; 56.4 at accessory rail | Toyota 2024 e-brochure |
| Ram 1500 2019 to present | not labeled | not labeled; Ram prints 51 minimum and 66.4 maximum width | Ram 2026 specifications |
Compare the Silverado: its inside width of 71.4 sits next to a box listed at 72.0 long, which implies the box ends rest on top of the rails, outside that figure. The same holds for the Tacoma, where Toyota's 56.4 inches at the accessory rail is below Better Built's 63.0 inch mid-size box. The span at the rail top is still your own measurement.
Mounting and clearance
The UWS crossover installation manual, printed by CURT Group, sets the box on rail pads on top of the bed rails, hooks one J-hook under the lip of the rail on each side, and tells the installer to center the box and check that the open lid clears the cab. It also says never to exceed the vehicle manufacturer's recommended capacity.
Use it with
Check boxes and racks in the rack and toolbox tables, and bed numbers on each truck page. Covers that sit on the same rails are in the tonneau tables.
Sources
- Weather Guard, GM8061 Spec Guide (Weather Guard and Better Built truck boxes), 04/24
- Weather Guard, Truck Box Fit Guide, Rev F, 2025
- CURT Group and UWS, Crossover Truck Tool Box Installation Manual (TB-60)
- Ford, 2026 F-150 specifications, as recorded in the FitsMyTruck vehicle table
- Ford, 2025 Super Duty technical specifications, as recorded in the FitsMyTruck vehicle table
- Chevrolet, 2026 Silverado 1500 configurator, as recorded in the FitsMyTruck vehicle table
- Chevrolet, 2026 Colorado compare page, as recorded in the FitsMyTruck vehicle table
- Toyota, 2024 Tacoma e-brochure
- Ram, 2026 Ram 1500 Tradesman specifications, as recorded in the FitsMyTruck vehicle table