A quadcon is a small ISO container sized so that four units coupled together take up the footprint of one standard 20ft container. A typical dry-freight quadcon measures about 4ft 9in long by 8ft wide by 8ft high on the outside, weighs about 2,100 lb empty, and carries roughly 8,000 to 9,000 lb of cargo depending on the build. Because a coupled set travels exactly like a 20ft ISO box, quadcons move by ship, rail and truck without special equipment, which is why the U.S. military uses them in large numbers.
What is a quadcon container?
The name comes from the math: quad means four to a 20ft footprint, the same way three tricons or two bicons make up the same module. The U.S. Army’s transportation manual FM 55-65 describes the quadcon as a lockable, weatherproof, reusable, prefabricated container with a structural steel welded frame, ISO corner fittings for lifting, restraint and coupling, and a base that allows four-way forklift entry.
Each unit stands on its own: it has its own doors, its own lock points and its own CSC-style data plate. Coupled into a set of four with the interconnecting hardware, the group presents standard 20ft corner castings to cranes, spreaders and twist locks. As FM 55-65 puts it, four QUADCONs coupled together have the same dimensions as a standard 20-foot ISO container and are compatible with the 20-foot cell guides of a containership.
Quadcon dimensions and weights
Exact figures vary a little by manufacturer and variant. The table below shows a representative current-production dry-freight quadcon (Sea Box model SB812.0) alongside the figures the Army manual lists.
| Specification | Manufacturer datasheet (Sea Box SB812.0) | Army FM 55-65 |
|---|---|---|
| External length | 4ft 9 7/16in (1,459 mm) | 57 in |
| External width | 8ft 0in (2,438 mm) | 96 in |
| External height | 8ft 0in (2,438 mm) | 82 in listed for the EDSS variant |
| Internal dimensions | 4ft 6in L x 7ft 6 9/16in W x 7ft 5in H | not listed |
| Door opening | 4ft 5 1/2in W x 7ft 1 1/8in H | not listed |
| Tare weight | 2,120 lb (960 kg) | not listed |
| Payload | 9,040 lb (4,100 kg) | cargo capacity 8,000 lb |
| Max gross weight | 11,200 lb (5,080 kg) | not listed |
| Capacity | 258 cu ft (7.3 cu m) | not listed |
Two practical notes on those numbers. First, a lower-height USMC pattern (6ft 10in) also exists, so always check the data plate on used units rather than assuming the 8ft height. Second, the payload printed on the plate is a rating, not a promise about your load plan: weight must still be distributed and secured to the container’s lashing points.
How the coupling works
Quadcons connect side by side with interconnecting couplers that lock the corner fittings of neighboring units together; a typical new unit ships with three couplers and a storage bracket. Once four units are joined, the set is lifted and handled as one 20ft equivalent unit. That single fact drives most of the quadcon’s value: units can be packed and sealed by different teams at different times, then travel together through the intermodal system, then split up again for final delivery by forklift.
What quadcons are used for
The U.S. Armed Forces are the largest user, and FM 55-65 recommends them for contingency deployments because unit equipment can move in the same container that stores it at home station. Outside the military, the same qualities that suit a deployment suit any operation that needs weatherproof, forkliftable, stackable storage in tight spaces: telecom and utility sites, remote work camps, law enforcement and emergency management stores, tool and parts cribs on construction sites, and ships or offshore platforms where deck space is measured in inches.
Compared with its siblings, the quadcon trades cubic capacity for handling flexibility. If you are choosing between the three formats, our tricon vs quadcon vs bicon comparison covers the decision in detail, and our guide to who actually stocks these units in the U.S. explains why quoted lead times differ so much between suppliers.
What to check before you buy
- Data plate and certification. Confirm the CSC-style plate is present and legible, and that the rating matches your transport plan.
- Couplers. Sets are often sold without the interconnecting hardware. If you intend to ship coupled, confirm couplers are included and matched.
- Door configuration. Single-end, double-end and shelved variants exist; make sure the access pattern fits how you will load.
- Height variant. 8ft and 6ft 10in patterns both circulate in the surplus market.
- Condition grade. The same one-trip, cargo-worthy and WWT logic that applies to full-size boxes applies here; our container grades guide explains what each grade means.
Sourcing quadcons in quantity
Lummid supplies quadcons on a build-to-order basis rather than from stock: units are manufactured to your order and then shipped, so production and transit time needs to be part of your project schedule. If your dates are firm, start the conversation early so the build can be scheduled ahead of when you need the boxes on site.
For bulk military and specialty ISO requirements, see our military containers page, or request a wholesale quote and tell us the quantity, door configuration and delivery points you need.
Sources
- Sea Box SB812.0 quadcon data sheet (dimensions, weights, capacity, couplers)
- U.S. Army FM 55-65, Appendix E (quadcon description, 20ft coupling, cell-guide compatibility)
