Sea Can vs Conex vs ISO Container Naming Canada

By Paul LeBlanc, owner, and Christian LeBlanc, second-generation operator, Van Blanc Ent. Inc.

Sea can, conex, ISO container, and shipping container are four names for one product: a steel intermodal box built to the ISO 668 standard. Sea can is the Canadian word, conex is the American military word, ISO container is the engineering word, and shipping container is the international word. The CSC plate proves they share one build.

Container terminology is one of the most common reasons a buyer calls our Brantford yard confused. A homeowner reads three websites and ends up wondering whether they need a “sea can” for backyard storage, a “conex box” because that is what the contractor said, an “ISO container” because the engineer’s email used that term, or a “shipping container” because that is what the bank financing form called it. The honest answer is that those four words describe the same physical object in 99 percent of real-world Canadian purchases. The differences are historical and regional, not structural.

Paul LeBlanc has been in the trade for 40 years, the last 19 of those running containers specifically. He hears the terminology question almost daily. “People think we are selling four different products. We are selling one product with four names. The trick is knowing which name your insurance company wants on the invoice, which name your transport broker wants on the customs paperwork, and which name your municipal building official wants on the permit application. The container itself does not change.”

Where Does the Term Sea Can Come From?

Sea can is the most common everyday term across English-speaking Canada. The history is genuinely Canadian. Sea-Can Containers Ltd. was founded in 1976 in Edmonton, Alberta. The company started in industrial wood products (crates, pallets, crane pads) and grew into one of the largest shipping container suppliers in Western Canada. As Sea-Can Containers expanded across the Prairies through the 1980s and 1990s, the brand name fell into common speech and lost its capitalization. By the time the Alberta oil patch was using sea cans for tool storage on every drill site, the term had become generic.

This is the same linguistic pattern that produced “kleenex” (for facial tissue), “xerox” (for photocopies), and “band-aid” (for adhesive bandages). A successful brand becomes the everyday noun for the category. Sea-Can Containers Ltd. still operates today as a recognised supplier, but the lowercase “sea can” has long since escaped trademark control and is the dominant Canadian term for any shipping container in any size, in any condition, used for any purpose.

Two important notes about how Canadians use the term in 2026:

• “Sea can” is the dominant term in Western Canada and Ontario. In Alberta, Saskatchewan, Manitoba, and Ontario, “sea can” is the term you will hear from contractors, farmers, oil-patch operators, and homeowners. If a supplier in Calgary, Edmonton, Saskatoon, Winnipeg, Toronto, or Brantford says “sea can,” they mean a shipping container.
• “C can” is a regional shortcut. In some Ontario and Western Canada conversations you will hear “c can” or “see can,” which is just a shortened spelling of “sea can.” Same product. Same dimensions. Same CSC plate.

What you will not hear: anyone in Canada calling a 20ft or 40ft container a “conex” unless they served in the US military or grew up watching American construction shows. The Canadian default is sea can.

What Is a Conex Box, and Why Do Americans Say It?

Conex is the American term, and it carries a specific military pedigree. The US Army developed the Transporter (the direct ancestor of the conex) for the Korean War in 1952 as a way to move supplies forward without losing material to pilferage and weather damage. The Container Express system, shortened to CONEX, replaced the Transporter in 1952 and became standard US military supply infrastructure through the Vietnam War. CONEX boxes were smaller than the modern 20ft (often 8.5 feet long), built heavier, and designed to be lifted by deck cranes from Liberty ships.

When the modern intermodal container revolution happened in the late 1950s (Malcolm McLean’s Sea-Land company is the usual reference point), the commercial industry diverged from the military’s CONEX program. The military kept the CONEX terminology and eventually moved to MILVAN and TRICON boxes. The civilian world moved to “container” and “ISO container.” But the word “conex” stuck in American English as a generic term for any intermodal-style metal box, especially in regions where US military presence shaped the local language.

In Canada in 2026, “conex” is rare. You will hear it occasionally in Pacific Northwest Canadian conversations because of cross-border industry overlap with Washington, Oregon, and Idaho. You will hear it in defence-adjacent supply chains where Canadian Forces work with American counterparts. Outside those niches, no Canadian buyer asks our Brantford yard for a “conex box.” They ask for a sea can.

The practical implication for Canadian buyers: if an American website is the source of your shipping-container research, “conex” is the word they will use. It means the same thing as “sea can” to us. There is no functional difference in the steel.

What Is an ISO Container (ISO 668)?

ISO container is the engineering term. It refers to a box built to the ISO 668 standard, which is the international classification system for intermodal freight containers. ISO 668 was first published in 1968 by the International Organization for Standardization in Geneva, and it specifies the external and internal dimensions, the corner casting positions, the minimum door opening sizes, and the weight ratings for every “Series 1” freight container in commercial use today.

The reason ISO 668 matters in real life is corner casting alignment. The standard sets the corner casting positions so that any 20ft and 40ft container built anywhere in the world will stack, lock, and ride on the same trailers, vessels, and rail flats. A 20ft built in Shanghai in 2018 will twist-lock perfectly onto a 40ft built in Antwerp in 2003 because both are built to ISO 668. That interchangeability is why the global container trade works at all.

Three details about the ISO 668 standard that come up in Canadian buying decisions:

• Nominal length differs from actual length. A 20ft ISO container is actually 19 feet 10.5 inches long. A 40ft ISO container is exactly 40 feet long. The 20ft is undersized so two of them, with twist-locks, equal one 40ft. That is how the corner castings line up when stacked.
• Standard heights are 8 ft 6 in and 9 ft 6 in. The 8 ft 6 in box is the original “standard” container. The 9 ft 6 in box is the High Cube. Both are ISO 668 compliant.
• ISO 6346 is the companion standard for marking. ISO 6346 is what gives every container its 11-character serial code (four letters plus seven digits plus a check digit). When an insurance broker asks for the container number, they are asking for the ISO 6346 marking, not the dimensions.

If your bank, your insurer, your engineer, your municipal permit office, or your customs broker asks for an “ISO container” or “ISO 668 container,” they are asking for a standard 20ft or 40ft shipping container with a valid CSC plate. Every Cargo Worthy and One-Trip unit at our Brantford yards meets that definition, and the single-voyage units that arrive in near-factory condition carry the freshest plates of all. Sea can = ISO container in 2026 Canadian buying.

When Should You Just Say Shipping Container?

“Shipping container” is the international neutral term. It is what the BBC says, what Reuters says, what the World Shipping Council says, and what your Canadian newspaper says when describing the global supply chain. It is also what most Google searches use, which is why our service-area pages at Van Blanc are titled “shipping containers” rather than “sea cans.”

Practically, “shipping container” is the safest term to use when:

• You are writing a customs declaration or international transport document
• You are filling out a Canadian municipal building permit form (most clerks recognise “shipping container” universally)
• You are talking to a non-trade professional (lawyer, accountant, banker, real-estate agent) who is not familiar with the slang
• You are searching online for buying advice (the term has the most consistent results)

And it is what Van Blanc uses on our website for the same reason. When a Brantford homeowner searches for “shipping container Brantford” or a contractor searches for “shipping containers Ontario,” they find our yard. If we titled the same page “sea cans” we would miss the searches from people who learned the terminology online or from American sources.

For a fuller treatment of what physically distinguishes the different grades and configurations behind the names, see how one box splits into Cargo Worthy, One-Trip, and reefer stock.

Which Container Term Is Used Where in Canada?

Container language is not random. It tracks the trade routes, the military presence, and the brand penetration of the last 70 years. Here is the regional 2026 vocabulary as we hear it at our Brantford yards:

• Sea can: dominant across Canada (Atlantic to Pacific), and in the US Pacific Northwest (Washington, Oregon, sometimes northern California). Strongest in Western Canada because Sea-Can Containers built the brand in Alberta first.
• Conex / conex box: dominant across the continental United States, especially in southern states, military communities, and rural America. Rare in Canada outside cross-border industry.
• ISO container: used in engineering documents, customs paperwork, insurance schedules, structural drawings, and academic publications. Almost never used in casual conversation.
• Shipping container: universal international term. Default in media, Google searches, manufacturer specifications, and bank or municipal forms.
• C can / see can: regional Canadian shortcut for “sea can.” Heard in Alberta, Saskatchewan, and parts of Ontario.
• Cargo container: used by trucking and freight forwarders, especially American ones. Synonymous with shipping container.
• Intermodal container: used by railways (CN, CP, Union Pacific, BNSF) and port operators. Refers specifically to a container designed to move between ship, rail, and truck without unloading.
• Storage container: used by the end-use market (the buyer who wants the box for backyard storage, ranch storage, or construction-site storage). Same physical product.

The takeaway: regional vocabulary tells you something about the speaker’s background. It does not tell you anything different about the metal.

What Is the CSC Plate, and Why Does It Unify the Names?

The reason sea can, conex, ISO container, and shipping container can all describe the same physical object is the CSC plate. The International Convention for Safe Containers was adopted in 1972 by a joint UN and International Maritime Organization conference in Geneva, came into force in 1977, and requires every intermodal freight container in active international trade to be approved and physically marked with a CSC safety approval plate. Canada implemented the convention through the Safe Containers Convention Act and the Safe Containers Convention Regulations.

The CSC plate is the rectangular metal plate (typically aluminum, sometimes steel) riveted to the outside of the left door of every container that has ever been in marine service. It is roughly 145 mm by 200 mm. The words “CSC SAFETY APPROVAL” are stamped at minimum 8 mm letter height. The other data (country of approval, manufacturer, manufacturing date, max gross weight, allowable stacking weight, and next inspection date) is at minimum 5 mm letter height.

The CSC plate is what proves that any container, regardless of which generic name your supplier used, was built to ISO 668 dimensions, passed the structural tests required by the convention, and is legally allowed to move in international intermodal trade. A box without a CSC plate is technically not a shipping container in the legal sense. It is a fabricated metal box.

What this means for Canadian buyers in 2026:

• The CSC plate is the only proof that matters. Whoever called the box a sea can, conex, ISO, or shipping container, the CSC plate is the unifying evidence that the unit was built to global standards.
• Read the CSC plate before paying. The plate tells you the year built, the country of origin, the manufacturer, and the max gross weight rating. We walk every buyer through the plate at our Brantford yards.
• An expired CSC plate does not mean the container is unsafe. A container that has aged out of marine service (typically after 30 to 40 years) can still be perfectly safe for ground-level Canadian backyard or construction storage. The plate just means the unit has retired from international shipping.
• No CSC plate is a yellow flag. If a seller has stripped or covered the CSC plate, ask why. Sometimes it is just paint. Sometimes the unit was never built to the convention.

If you want the full pre-purchase routine, our step-by-step checklist for inspecting a used unit covers how to read the CSC plate, the floor, the corner castings, and the doors before you pay.

When Does the Container Name Actually Matter (Insurance, Transport, Customs)?

For 99 percent of Canadian residential and small-business buyers, the terminology does not matter at all. You order a sea can, we deliver an ISO 668 compliant shipping container with a CSC plate, and everyone is happy. The terms are interchangeable in everyday Canadian commerce.

The 1 percent where terminology does matter is paperwork. Three specific scenarios:

• Insurance schedules. If you are insuring the container as part of a commercial schedule (farm policy, construction policy, business contents policy), the insurer will often want the formal description “ISO 668 freight container, 20ft Cargo Worthy, container ID [ISO 6346 code].” That language is unambiguous and meets the underwriter’s terminology. If you say “sea can” on the insurance form, the broker will translate it for you, but the policy itself uses the engineering term.
• Transport and customs documents. If the container is moving across the Canada-US border, or being imported direct from China to your delivery address, the customs forms (CBSA, US CBP) want “container” or “intermodal freight container” plus the ISO 6346 number. “Sea can” on a customs form will get questioned. Use the formal name.
• Engineering and official documents. Any drawing or formal submission an official body reviews should use “shipping container” or “ISO container” with the dimensions, not “sea can.” An engineer’s structural review of a container build will always use ISO 668 terminology because the structural assumptions in the standard are what the engineer is calculating against.

For everything else (the phone call to the yard, the conversation with the delivery driver, the chat with your neighbour over the fence), sea can, conex, ISO, and shipping container are completely interchangeable. Use whatever word lands naturally.

Is a “Vintage Conex” on Facebook Marketplace a Scam?

One specific scam pattern uses naming confusion to bait Canadian buyers. We have seen this pattern grow in 2025 and 2026 across Ontario Facebook Marketplace, Kijiji, and Instagram.

The setup looks like this. A listing appears for a “vintage Conex box, original US Army,” priced far below the going rate for a real container, with free Ontario delivery promised this weekend. Photos show a small olive-drab box that looks plausibly military. The seller says they have one or two left and need to move them fast. They ask for an e-transfer deposit to “hold” the unit and confirm the delivery slot. The container never arrives. The seller stops replying.

Three things to know about this scam:

• True 1950s Korea-era Conex boxes are 75-year-old collectibles. Any genuine original Korean War or Vietnam War CONEX is rare, sought after by military collectors, and worth far more than a standard modern container. A listing priced well below the market is the giveaway.
• “Vintage Conex” in Canada is almost always either a modern repaint or a flat scam. A standard 20ft modern shipping container painted olive drab is not a vintage conex. It is a sea can wearing a costume.
• The honest test still applies. Can you drive to the seller’s physical yard, walk the row, read the CSC plate, and inspect the unit before paying? If no, the deal is not real. The Facebook box is the dominant container scam in the Ontario market.

Van Blanc holds 200+ units across four Brantford yards. You walk the row, read the CSC plate, and pick the specific container before you pay from the inventory you can stand in front of. That is the strongest protection against terminology-based scams in this market. If you want to see how these listings are baited, our breakdown of the deposit tricks that target Ontario buyers goes deeper than this one section can.

What Do 40 Years in the Trade Teach About Container Naming?

Paul LeBlanc’s perspective on the naming question is shaped by four decades of watching the language drift. “When I started in the trade in the mid-1980s, the word in Ontario was ‘shipping container’ because that is what the manufacturer paperwork said. Through the 1990s, as the Alberta oil patch grew and Sea-Can Containers got bigger and bigger, the word ‘sea can’ came east. By the early 2000s every farmer in southwestern Ontario was calling them sea cans. The American conex thing never really took hold here. The newest term I hear is just ‘container,’ shortened because everyone knows what you mean by context. That is what happens when a product becomes common. The name simplifies.”

Christian LeBlanc, who runs the shipping side at Van Blanc and is Paul’s son, sees the next generation of the same drift. “Our online inquiries from buyers under 35 mostly use ‘shipping container’ because that is the search term. Phone inquiries from buyers over 50 mostly use ‘sea can’ because that is the trade word. Engineers and architects use ‘ISO container’ because that is the spec language. We answer all three the same way. We hold 200+ of them, you pick the one you want, and the CSC plate proves what you are buying.”

For terminology research beyond this article, the rest of the trade vocabulary (Cargo Worthy, One-Trip, Wind and Water Tight, High Cube, reefer, flat rack, open top, and the others) is defined in our plain-language vocabulary reference. If your next question is how big each box actually is, the measurements behind every name are laid out in detail, and the grades and configurations sit in our rundown of the grades you can actually buy.

Frequently Asked Questions: Sea Can, Conex, ISO, Shipping Container Terminology

Sources and Further Reading

• ISO 668 (Series 1 Freight Containers, Classification, Dimensions and Ratings, Wikipedia summary)
• ISO 668:2020, Series 1 freight containers, Classification, dimensions and ratings (International Organization for Standardization)
• ISO 6346, Freight containers, Coding, identification and marking (Wikipedia summary)
• International Convention for Safe Containers (CSC), International Maritime Organization
• Safe Containers Convention Regulations (SOR/82-1038), Justice Laws Canada
• Sea-Can Containers Ltd. company history (Edmonton, founded 1976)
• Canadian Anti-Fraud Centre, online sale fraud reporting

Related Reading

• How big each size really is
• Telling the grades apart
• What to check before you pay
• The rest of the trade words