Unboxing the Buyers Products Diamond Tread Aluminum Underbody Truck Box

Bed space is the thing you run out of first on a work truck. Every box you set in the bed is bed you can't use, and a crossover eats the front two feet before you've loaded anything.

An underbody box costs you none of it. It hangs off the frame rail below the bed, out of the way, out of your sight lines, and low enough that it doesn't affect how the truck handles. The catch is that fitting one depends entirely on what's already under there — which is why measuring matters more than the spec sheet.

Buyers Products diamond tread aluminum underbody truck box

This unboxing covers the Buyers Products 36-in x 18-in x 18-in Diamond Tread Aluminum Underbody Truck Box (1705105) — how it ships, what's inside, real measured dimensions, and the one thing you have to buy separately.

About Buyers Products

Buyers has been building truck equipment since 1946 — eighty years in the business. A large share of their line is made in the USA, including this box. You've seen these on the road whether you registered it or not; they're the boxes hanging under half the flatbeds in the country.

How it ships

This one arrived in a standard cardboard carton with molded paper dunnage inside. The packaging is noticeably bigger than the box itself, which is deliberate — that gap is what protects the corners in transit. Ours showed up in good condition.

Shipping method depends on size. Larger underbody boxes go LTL freight on a pallet, which means a delivery appointment. Smaller ones like this 36-inch can often go parcel through UPS or FedEx. Worth checking before you order if you don't have a dock.

The build

.100-inch diamond tread aluminum. That's the thing to understand about this box. You get protection comparable to a steel underbody box, but at aluminum weight — and aluminum doesn't rust. That matters a lot on a box mounted directly in the road spray path, where you never see the underside to catch a chip before it starts.

A few details worth noting:

• Compression latch — lift and twist left to open. It pulls the door tight against the seal rather than just holding it shut
• Replaceable gasket, and a good one. Keeps moisture, dust and road debris out. Being replaceable means a box that starts leaking in year four is a ten-minute fix, not a new box
• Hidden hinge — the door opens almost all the way even with the box sitting on a flat surface, so you don't need clearance below the box to open it
• Aircraft-grade cables hold the door open against the body
• Structural rib in the door — there's no flex in it, which is what stops a pry bar from finding purchase when it's closed and locked
• Drop-down door, standard for underbody boxes since they usually sit at or below waist height. Buyers also makes top-opening versions for boxes mounted higher, around shoulder height

What's inside the box

• Toolbox mounting instructions, including part numbers for the mounting brackets you'll need and for replacement latches and accessories
• Warranty information — Buyers covers most of their products with a one-year warranty, with extended coverage on a few specific lines
• Two keys, tucked at the back of the box. There's a key code stamped on the key that matches the lock, so replacements are easy if you lose them. Keep one on the keychain and one somewhere safe

Measured dimensions

We put a tape on it, because listed dimensions and usable space aren't the same thing.

Exterior — exactly 36" wide x 18" high x 18" deep. The listed dimensions are the real dimensions, which isn't always the case.

Door opening — 32 and 1/4 inches wide, 14 and 7/8 inches tall.

Interior — roughly 35 and 3/4 inches wide and just under 18 inches tall, about two tenths less than the exterior thanks to the aluminum thickness. Depth is where it differs most: 16 and 1/2 inches, because the door frame protrudes into the space.

If you're planning around a specific case or tool, that 16.5-inch interior depth is the number to work with, not 18.

The part people forget: mounting brackets

No mounting hardware is included with this box. None. If you're hanging it under a flatbed, you need mounting brackets, and they're sold separately.

The brackets correspond to the height and depth of the box, so this 18 x 18 box takes the 18-inch brackets. The part numbers are printed in the instruction sheet inside the box, but budget for them at order time rather than discovering it on install day.

Sizing it to your truck

Buyers offers this style in widths from 14 inches up to 72 inches, plus other depths and heights.

The number one rule with underbody boxes: measure the mounting location first. Get under the truck and find the continuous clear length of frame rail where you want it, then note everything in the way — fuel tank, DEF tank, exhaust, spare tire winch, air tanks. Buy the box that fits that space, not the biggest one that sounds good.

Not sure what you're looking at down there? Send us a photo and a measurement and we'll tell you what fits.

Shop the Buyers Products 36 x 18 x 18 Diamond Tread Aluminum Underbody Truck Box

Same size, different configuration:

• 36 x 18 x 18 with a 3-point latch (1735105) — much harder to pry, and it seals better along the full door
• 36 x 18 x 18 with double barn doors (1705205) — reach straight in instead of over a drop-down door
• 36 x 20 x 18 with a drawer (1712205) — organized small parts up top, bulk below
• 36 x 24 x 24 (1705135) — more volume, but check your ground clearance

Browse the full range of underbody boxes to compare sizes and materials.

FAQ

Does this box come with mounting brackets?
No. Brackets are sold separately and correspond to the height and depth of the box, so an 18 x 18 box takes 18-inch brackets. Part numbers are in the instruction sheet inside the box.

How thick is the aluminum?
.100 inch diamond tread aluminum — protection comparable to steel, at a lower weight, and it won't rust.

What are the actual interior dimensions?
Roughly 35 3/4 inches wide, just under 18 inches tall, and 16 1/2 inches deep. The depth is less than the exterior because the door frame protrudes into the space.

Does it come with keys?
Two, with a key code stamped on the key that matches the lock, so replacements are straightforward.

Will it ship freight or parcel?
Depends on size. Larger underbody boxes go LTL freight with a delivery appointment; smaller ones like this 36-inch can often ship parcel via UPS or FedEx.

What's the warranty?
Buyers covers most of their products with a one-year warranty. A few specific lines carry extended coverage.

Can I mount it on top of a flatbed instead of underneath?
Yes. These are most commonly mounted under a flatbed, but top mounting works too. The hidden hinge means the door still opens almost fully even sitting on a flat surface.

What size should I get?
Measure your mounting location first and buy the box that fits it. Buyers makes this style in widths from 14 to 72 inches.

Looking to upfit your van or truck and get it ready for work? Our US-based upfit pros are ready to help — call, text, chat or email.