Shipping Container Types Explained: Standard, High Cube, Open Top, Flat Rack and Tank

When you book sea freight from China, the quote usually names a box: “20′ GP” or “40′ HC.” Most first-time importers treat that as a formality and let the forwarder pick. But the container type decides whether your cargo can be loaded at all, whether it attracts an out-of-gauge surcharge, how it is lashed, and how fast it clears the yard at Chattogram. Getting it wrong means a re-booking, a missed sailing, or a load that has to be stripped and re-packed at the origin CFS. This guide walks through the box types a Bangladeshi importer actually encounters and when each one is the right call.

The dry van: standard 20ft and 40ft containers

The general-purpose (GP) dry container is the default for almost everything: garments, hardware, packaged food, machinery that fits through a standard door, and consolidated LCL cargo. It is a sealed steel box that loads through doors at one end. The widely quoted internal capacities are roughly 33 cubic metres for a 20ft and about 67 cubic metres for a 40ft, but you should never plan a load to the last centimetre against a generic figure — the usable volume drops once you account for pallet footprints, bracing, and the fact that cartons do not stack to the ceiling without crushing. Confirm the exact internal length, width, door opening, and maximum payload on the container’s CSC plate and your carrier’s equipment sheet before you finalise a packing plan.

The payload limit matters more than importers expect. A 20ft box is often the wrong choice for dense cargo such as tiles, stone, batteries, or steel parts: you will hit the weight ceiling with the container half full, and you have paid for volume you cannot use. For dense goods, a part-loaded 40ft or an LCL booking is frequently cheaper per tonne. For light, bulky goods such as furniture or plastic housewares, the opposite is true — you run out of space long before weight, and a high cube earns its keep.

High cube: the extra foot of height

A high cube (HC) container is the same length and width as a standard 40ft but roughly 30 cm taller, giving around 76 cubic metres. On paper that is a modest gain; in practice it is the difference between stacking one more layer of cartons or one more tier of furniture across the whole floor, so the extra volume compounds. Most 40ft equipment moving on the China–Bangladesh trade today is HC by default, and the freight rate is usually the same or only marginally higher than a standard 40ft. The one thing to check is delivery: an HC on a road chassis sits higher, which can matter for a low godown gate or a covered loading bay. Measure your gate clearance before the container leaves the port.

Open top: when the cargo loads from above

An open-top container has a removable tarpaulin roof supported by bows instead of a fixed steel top. You use it when the cargo is too tall to pass through the end doors but still fits within the container walls — a tall printing press, a piece of tank equipment, a machine on a frame. It is loaded by crane from above, then sheeted and roped down. Two consequences follow. First, if the cargo sits above the top rail it becomes out-of-gauge (OOG) and attracts a surcharge plus restrictions on where it can be stowed on the vessel. Second, the tarpaulin is not watertight the way a steel roof is, so moisture-sensitive goods need their own weatherproofing inside. Open-top equipment is also less common, so book it early — a last-minute open-top request is a frequent cause of rollover.

Flat rack: over-width and over-height loads

A flat rack is a container floor with two end walls and no sides or roof. It carries loads that exceed the width or height of a normal box: a wide industrial fan, a boat, a transformer, construction equipment, long steel sections. Flat racks can be loaded from the side or top and the cargo is bolted, welded to lashing points, or chained down. Anything wider than the rack, taller than the end walls, or heavier on a point basis is OOG, and the carrier will quote a multiplier — often the cargo is rated as occupying two or more container slots because nothing can be stacked on it. For a Bangladeshi importer bringing in a single large machine, the honest comparison is flat rack versus break bulk versus dismantling the machine to fit a standard box; the right answer depends on the machine, and it is worth pricing all three.

Read our companion guide on break bulk cargo if your load is genuinely oversized, and the 20ft vs 40ft comparison if you are choosing between standard sizes.

Reefer, tank and other specials

A reefer (refrigerated container) is an insulated box with an integral cooling unit that plugs into the vessel and the terminal. It carries anything temperature-controlled — food, pharma, some chemicals — and it is booked and priced quite differently from a dry box, including plug monitoring fees and tighter free time. We cover it in detail in reefer container shipping explained. A tank container (ISO tank) is a cylindrical vessel in a frame for bulk liquids and is almost always arranged by a specialist. Ventilated, insulated (non-powered), and bulk containers exist for specific commodities such as coffee or grain but rarely feature in general China–Bangladesh trade.

How the box type shows up in customs and costs

The HS code and duty on your goods do not change with the container type — classification follows the product, not the packaging. What changes is the freight side of your landed cost. OOG cargo on flat racks and open tops carries surcharges, sometimes slot multipliers, and occasionally a longer dwell at the port because it needs special handling equipment to lift off. Detention and demurrage clocks still run, and a flat rack often has shorter free time because the equipment is scarce. Build these into your total landed-cost calculation rather than discovering them on the arrival invoice.

Common mistakes to avoid

• Booking a 20ft for dense cargo and hitting the weight limit with the box half empty — price it per tonne, not per box.
• Assuming any 40ft is a high cube. Confirm on the booking; if you planned the load for HC height and a standard box turns up, a layer does not fit.
• Requesting an open top or flat rack at the last minute. Special equipment is limited and late requests get rolled to the next sailing.
• Forgetting gate and bay clearance at your own godown for an HC on a chassis.
• Not weatherproofing cargo inside an open top — the tarpaulin is not a steel roof.
• Treating an OOG surcharge as a surprise. Ask the forwarder to quote it upfront when the cargo is clearly over-dimension.

Container age, condition and grade

Containers are not all equal even within a type. Boxes are graded roughly as new (one-trip), cargo-worthy, wind-and-watertight, and as-is. For most sea freight bookings you do not choose the grade — the carrier or NVOCC allocates whatever is in the depot — but you can and should inspect the unit at stuffing. Walk inside with the doors closed and look for pinholes of daylight in the roof and corners, check the floor for soft or oil-stained boards, run the door gaskets, and confirm the doors close and the locking bars seat without forcing. A leaking roof on a monsoon voyage ruins cartons stacked to the ceiling, and the claim conversation months later is far harder than rejecting the box on day one. Photograph the container number, the CSC plate, and the interior before loading.

If you are buying a container outright — for a site store, a container cold room conversion, or a godown extension — then grade is a price and fitness decision you make directly, and a one-trip or cargo-worthy unit is worth the premium over an as-is box that may need welding.

Weight, VGM and why the box matters

Every packed container must have a Verified Gross Mass declared before it can be loaded on the vessel — the total of cargo, dunnage, and the container’s own tare weight. The tare is stamped on the door and differs by type: a reefer and a flat rack are heavier empty than a dry van, so the same cargo in a heavier box leaves less room under the road and vessel weight limits. If you are near a payload ceiling with dense goods, the container type you pick directly changes how much product you can legally load. We cover the declaration itself in VGM explained.

Not sure which box your cargo needs? Send us the dimensions and weight of your largest piece and we will tell you whether it fits a standard container, needs special equipment, or should move as break bulk — and what each option costs for your route. Start with our freight and sourcing services, talk to us through the contact page, or use our China sourcing and buying agent service if you also need help placing the order. You can also browse ready equipment in our shop.