Key takeaways
- Six best truck tool boxes for full size trucks compared by style, length, capacity and fit, from saddle boxes to slim crossovers and chests.
What's inside
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The Weather Guard 121-5-04 Saddle Box is the best overall truck tool box for a full size truck on this list: it is a low-profile aluminum box rated at 11.0 cubic feet, and its saddle design drapes over the bed rails so it uses space you would otherwise lose. If you want a cross-bed box with more length and a luggage rack, the COOLBAG 70-inch is the next stop, and the Northern Tool slim box suits drivers who want to keep the rear window clear. “Full size” here means pickups like the F-150, Silverado, Ram 1500 and Tundra, where the bed is wide enough for a crossover or chest-style box.
Quick List
- Weather Guard 121-5-04 Saddle Box – best for maximum low-profile capacity
- COOLBAG Crossover 70-Inch – best for long beds and a luggage rack on top
- Tradesman 7511101 70-Inch Slimline – best for a shallow cross-bed box that preserves rear visibility
- COOLBAG Crossover 63-Inch – best for narrower beds, RVs and trailers
- Weather Guard 634-5-04 All-Purpose Chest – best for sitting low in the bed under a tonneau or cap
- Northern Tool Slim Crossover – best for a narrow, low-profile box that keeps the rear window clear
Which One Is Right for You?
| If you… | Choose |
|---|---|
| Want the most capacity without raising the box high above the rails | Weather Guard 121-5-04 Saddle Box |
| Carry long items and want a rack on top of the box | COOLBAG Crossover 70-Inch |
| Care most about rear-window visibility on a full size bed | Tradesman 7511101 Slimline |
| Have a narrower bed or want a box you could also use on an RV or trailer | COOLBAG Crossover 63-Inch |
| Use a tonneau cover, truck cap or bed lid | Weather Guard 634-5-04 All-Purpose Chest |
| Want a slim crossover profile and paddle latches | Northern Tool Slim Crossover |
The first decision is the shape of the box, not the brand. Crossover and saddle boxes sit on the bed rails and are the best match for open beds, while chest boxes sit between or below the rails and play better with covers. Measure your bed rail width and the clearance under any cover before ordering.
All 6 Picks in Detail
1. Weather Guard 121-5-04 Saddle Box – Best for Low-Profile Capacity
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A saddle box is a crossover-style box that drapes over the bed rails so part of the box sits outside the bed and the center stays low. Weather Guard’s 121-5-04 is a full-size, low-profile aluminum model in gloss black with an 11.0 cubic foot capacity. Retailer pages list overall dimensions of about 72 inches long, 20 inches wide and 18 inches high, with a bottom section close to 58.5 inches across, but treat those as figures to confirm on the product page. It suits contractors, tradespeople and weekend drivers who want serious storage that still allows decent rear visibility.
- Material: aluminum, gloss black finish
- Capacity: 11.0 cubic feet per the listing
- Style: low-profile saddle box for full size trucks
- Reported overall size: about 72 x 20 x 18 inches per retailer pages (confirm on listing)
- Weight: retailer pages report roughly 76 to 82 pounds (confirm on listing)
Pros:
- Largest stated capacity on this list
- Saddle shape keeps the profile lower than a conventional bed-wide box
Cons:
- Check that your truck’s rail width and any rail caps allow saddle fitment
- Less suitable if you plan to run a tonneau cover over the bed
Compared with the Weather Guard 634-5-04 chest, it gives more capacity but sits higher, so it trades cover compatibility for room.
2. COOLBAG Crossover 70-Inch – Best for Long Beds and a Rack
The COOLBAG 70-inch crossover is a bed-wide aluminum box measuring 70 x 20 x 15 inches per the listing name, with a 5-bar tread pattern, a waterproof claim, a lock and a luggage rack on top. It suits drivers who want to carry both tools and bulky gear, since the top rack can hold straps, a cooler or a small load. The listing mentions pickups and trucks, so check the length against your bed width before ordering. Because it is a crossover box, it mounts across the bed rails and is not designed to go under a tonneau cover.
- Size: 70 x 20 x 15 inches per the listing name
- Material: aluminum with a 5-bar tread pattern
- Weather resistance: described as waterproof; confirm the sealing method on listing
- Security: lockable; confirm lock and latch type
- Extra: luggage rack on top of the box
Pros:
- Long width suits larger full size beds
- Top rack adds a carrying surface
Cons:
- Not intended for use beneath a tonneau cover
- Load rating for the rack is not stated in the listing name
It is a more utilitarian, rack-equipped alternative to the Tradesman slimline.
3. Tradesman 7511101 70-Inch Slimline – Best for Rear Visibility
The Tradesman 7511101 is a 70-inch black slimline cross-bed box made for full size trucks. The word “slimline” signals a shallower profile than a standard crossover, which helps with the rear window view and with side-mounted gear. The listing name does not give depth, height, capacity or material details, so treat it as a style of box rather than a spec-heavy product and confirm the numbers before buying. It fits drivers who want secure bed storage that does not dominate the bed.
- Width: 70 inches per the listing name
- Style: slimline cross-bed box, black
- Fit: described for full size trucks
- Material and weight: confirm on listing
- Capacity: confirm on listing
Pros:
- Shallow profile preserves visibility
- Full-width coverage across the bed
Cons:
- Slim boxes generally hold less than deeper chests
- Few specifics in the listing name
Choose it over the COOLBAG 70-inch when height and visibility matter more than a roof rack.
4. COOLBAG Crossover 63-Inch – Best for Narrower Beds, RVs and Trailers
This COOLBAG model is the shorter sibling of the 70-inch box, at 63 x 20 x 15 inches per the listing name, with the same aluminum, waterproof, lockable and luggage-rack description. The listing text also mentions RV and trailer use, which makes it more flexible if you want to move the box between vehicles. It suits owners of full size trucks with narrower rail spacing and anyone who wants to leave some bed room on either side of the box. Always compare the 63 inches against your bed rail width, since a box that is too short will not span the rails.
- Size: 63 x 20 x 15 inches per the listing name
- Material: aluminum, black finish
- Weather resistance: described as waterproof; confirm on listing
- Security: lockable; confirm lock type
- Extra: luggage rack on top; mentions RV and trailer use
Pros:
- Shorter length fits more vehicle types
- Can serve double duty on trailers or RVs
Cons:
- May be too short to span wider full size bed rails
- Same unanswered rack load rating as the larger box
Pick it over the 70-inch version only after measuring; for most full size trucks, the wider box is the safer fit.
5. Weather Guard 634-5-04 All-Purpose Chest – Best Under a Tonneau Cover
Weather Guard’s 634-5-04 is an all-purpose chest rather than a crossover box. Manufacturer and retailer pages describe it as an aluminum chest with 10.0 cubic feet of capacity and dimensions around 58 x 20 x 19 inches, designed to fit between the wheel wells and sit below the bed rail so you can still use a tonneau cover or truck cap. That makes it the cleanest choice for drivers who need to keep a covered bed. The listing says it fits full size trucks in gloss black; the exact interior dimensions are not stated, so confirm them on the product page.
- Capacity: 10.0 cubic feet per the listing
- Style: all-purpose chest for full size trucks
- Reported size: about 58 x 20 x 19 inches per retailer pages (confirm on listing)
- Finish: gloss black aluminum
- Cover compatibility: designed to sit below the rails, per retailer descriptions
Pros:
- Works with many tonneau covers and caps
- Sits within the bed, so it stays out of the line of sight
Cons:
- Uses bed floor space that a crossover box does not
- Slightly less capacity than the saddle box
Unlike the saddle box, it is built for covered beds, so it is the better pick if your truck wears a lid.
6. Northern Tool Slim Crossover – Best Slim Crossover Profile
The Northern Tool slim crossover measures 69 x 12 x 13 inches per the listing and is made of low-profile aluminum in gloss black with paddle latches. The 12-inch width is narrow, which keeps it out of the way of the rear window and leaves bed room in front of it. That narrow footprint also means a smaller interior than the 20-inch-wide boxes, so it is aimed at drivers who carry a limited set of tools. Confirm capacity and hardware details on the product page, as the listing name does not include them.
- Size: 69 x 12 x 13 inches per the listing
- Material: aluminum, gloss black finish
- Latches: paddle latches, per the listing
- Style: slim, low-profile crossover
- Capacity and weight: confirm on listing
Pros:
- Compact footprint keeps the bed usable
- Paddle latches are straightforward to operate with gloves on
Cons:
- Narrow interior holds less than a 20-inch-wide box
- Not suitable for large power tools
It is the thinnest option here, so it makes the most sense next to the Tradesman slimline for buyers who put visibility first.
Specs Compared
| Model | Style | Size (L x W x H) | Material | Capacity | Extras |
|---|---|---|---|---|---|
| Weather Guard 121-5-04 | Low-profile saddle box | About 72 x 20 x 18 in per retailer pages; confirm on listing | Aluminum, gloss black | 11.0 cu ft | Full size fit |
| COOLBAG Crossover 70″ | Crossover | 70 x 20 x 15 in | Aluminum, 5-bar tread | Confirm on listing | Waterproof claim, lock, luggage rack |
| Tradesman 7511101 | Slimline cross-bed | 70 in wide; depth and height confirm on listing | Confirm on listing | Confirm on listing | Black, full size fit |
| COOLBAG Crossover 63″ | Crossover | 63 x 20 x 15 in | Aluminum, black | Confirm on listing | Waterproof claim, lock, luggage rack |
| Weather Guard 634-5-04 | All-purpose chest | About 58 x 20 x 19 in per retailer pages; confirm on listing | Aluminum, gloss black | 10.0 cu ft | Sits below rails |
| Northern Tool Slim Crossover | Slim crossover | 69 x 12 x 13 in | Aluminum, gloss black | Confirm on listing | Paddle latches |
How We Chose These
This guide is built from desk research, not physical testing. We began with the six listings supplied for the topic and compared what each listing states about length, depth, material, capacity and locking hardware. For the two Weather Guard models we also checked manufacturer and retailer descriptions of capacity and overall size. We grouped the products by mounting style, since a saddle, crossover and in-bed chest solve different problems, and we gave priority to full size truck fit, secure latching and weather protection. Wherever a listing does not give a number, the article says to confirm it on the product page rather than guessing.
What to Look For
Box Style: Crossover, Saddle, Chest or Side Mount
A crossover box spans the bed from rail to rail and is the classic choice for full size trucks. A saddle box is a crossover whose ends drape over the rails, which lowers the profile and uses space outside the bed. A chest sits on the bed floor, often between the wheel wells, and is the natural match for tonneau covers and caps. Side-mount boxes sit along one wall of the bed and leave the other side open. Pick the style that fits what else you put in the bed: if the bed also carries a cover, a lid or sheet goods, a chest or slim box is usually easier to live with.
Measure Your Bed Before You Choose a Length
Bed rail width on full size trucks commonly falls in the low-to-mid 60s of inches, but it varies by make, model year and bed liner, so a tape measure beats a spec sheet. Measure the outside rail-to-rail distance for crossover boxes and the distance between the wheel wells for chests, which on most full size beds is in the neighborhood of 50 inches. Allow for rail caps, stake pockets and any bed rail lighting. A good rule of thumb is to make sure the box is no longer than the rail width and that there is room for the lid to open without hitting the rear window or cab.
Worked example: if your rails measure 64 inches across, a 63-inch crossover will fit only if the mounting hardware clears the rail caps, while a 70-inch box will not fit as a flat crossover and would be better as a saddle design. For a chest, subtract the chest height from the bed wall height and confirm that your cover or cap still closes with room to spare.
Material, Tread Pattern and Weather Sealing
Aluminum is the standard material because it resists rust and keeps weight down. Tread-plate or 5-bar patterns add rigidity and grip, but the underlying gauge matters more than the pattern. Check for an overlapping or gasketed lid, drain holes where appropriate and a rubber seal around the lid. “Waterproof” is a marketing term; most truck boxes resist rain well but are not designed for submersion, and a box mounted at an angle can still collect water in the lid channel.
Latches, Locks and Security
Paddle latches are easy to use with gloves, while T-handle and compression latches provide a tighter seal. A box with a single lock and one latch may be easier to defeat than a multi-point system. Because truck boxes are exposed to theft, keep high-value tools out of the box overnight and use a bed-mounted cable if you leave valuable gear in the truck. Always confirm that the lock cylinder is keyed alike or replaceable, and keep a spare key somewhere other than the box.
Weight, Mounting and Drilling
Most boxes mount with clamps that grip the bed rail, so they need no drilling, though some manufacturers recommend drilling into the bed for permanent security. A 70-to-80-pound box adds to your payload, so subtract the box weight and everything inside from your truck’s payload rating. If you regularly carry heavy tools, keep the weight low and centered, and keep wiring or bed lights clear of the lid swing path.
Installation, Maintenance and Everyday Use
Most crossover and saddle boxes install with rail clamps and a few basic tools, and two people make the job far easier because even a mid-size box is awkward to hold in position while you tighten hardware. Set the box slightly forward of the rear of the cab so the lid clears the glass when it is fully open, and check clearance again with the bed fully loaded, since the suspension sits lower under load. Tighten the clamps again after the first week of driving, because vibration can loosen them.
For upkeep, rinse road salt and mud from the lid channel, wipe the rubber seal and add a light silicone spray to the hinges and latches once or twice a year. Keep the interior organized with small bins or a removable tray so heavy tools do not slide into the lid seal. If the box has a gas strut or support arm, check that it holds the lid open before you reach in, because a lid that falls shut is a real pinch hazard. Finally, keep the drain holes clear and avoid storing damp items, rags or leaking containers inside, which can cause corrosion and odors over time.
Questions
What size tool box fits a full size truck?
Crossover and saddle boxes commonly run from the low 60s to about 70 inches long, depending on the rail width of your truck. Chests that sit between the wheel wells are shorter, typically in the high 50s. Measure your own bed instead of relying on a general number.
Can I use a tonneau cover with a crossover tool box?
Usually not, because a crossover sits on top of the rails where the cover needs to rest. A low chest that sits below the rails, such as the Weather Guard 634-5-04, is the better match for a cover or cap.
Is a saddle box better than a standard crossover?
A saddle box can offer more capacity for the same height above the rails because it uses space outside the bed. A standard crossover is simpler and fits more rail styles, so the better choice depends on your truck’s rail design.
Are aluminum truck boxes truly waterproof?
Most are weather-resistant rather than fully waterproof. A rubber seal, a tight latch and a lid that sheds water help, but you should still keep sensitive items in sealed bags or bins.
Will a truck tool box block my rear window?
Taller boxes can. Slim and low-profile designs, such as the Northern Tool slim box and the Tradesman slimline, are meant to keep the rear view clearer, and a low-profile saddle design helps too.
How much weight can I put in a truck tool box?
The box’s own rating, where stated, and your truck’s payload rating are the two limits. Keep heavy items low and centered, and add the box weight to the load so you stay within the payload.
Do I need to drill into my truck bed to install a box?
Many crossover and saddle boxes use rail clamps and need no drilling, although some manufacturers recommend drilled mounting for a more permanent install. Check the instructions for your exact box and your bed liner type.
Should I choose a deeper box or a longer one?
Length is limited by your bed rails, so depth is the variable you can adjust. A deeper box holds taller items such as power tools, but it blocks more of the rear window, so balance capacity against visibility.
Update History
- October 20, 2026 – Initial publication; product set drawn from current catalog listings.
- Check the product page for current specifications and availability before buying.
Sources
- Manufacturer product and specification information for Weather Guard
- Retailer listing titles and specification fields for all six products
- General truck bed measuring and payload-rating practice, used for the sizing advice