Encyclopedia of Container Types: Parameter

Data Source: ISO 668:2020 standard, container type parameter tables on shipping company official websites

The core of container transport lies in the "box". Different cargo requires different container types—choose the wrong type, and the cargo either won't fit, won't fill the container, or the freight cost is wasted. This article systematically reviews the types, parameters, and applicable scenarios of 8 common ocean shipping containers.

I. ISO Classification System for Containers

According to the ISO 668:2020 standard, ocean shipping containers are divided into three major categories by use and structure:

Classification	Description	Common Container Types
Dry Container	General sealed container, most commonly used	20GP, 40GP, 40HQ, 45HQ
Special Container	Special containers designed for specific cargo	Reefer containers, open-top containers, flat rack containers, tank containers, ventilated containers
Regional/Special Purpose	Dedicated to specific regions or industries	Garment containers, car containers, bulk containers

Note: The above is a simplified classification for practical operations; the official ISO standards (ISO 6346/ISO 668) provide more precise subdivision by container type code. This article focuses on the 8 most common container types in foreign trade practice.

II. Comparison Table of Parameters for 8 Main Container Types

Parameter	20GP Dry Container	40GP Dry Container	40HQ High Cube Container	40RH Refrigerated Container	20OT Open Top Container	20FR Flat Rack Container	ISO Tank Container	20VT Ventilated Container
External Length (mm)	6,058	12,192	12,192	12,192	6,058	6,058	6,058	6,058
External Width (mm)	2,438	2,438	2,438	2,438	2,438	2,438	2,438	2,438
External Height (mm)	2,591	2,591	2,896	2,896	2,591	2,591	2,591	2,591
Internal Length (mm)	5,898	12,032	12,032	11,590	5,898	6,028	—	5,898
Internal Width (mm)	2,352	2,352	2,352	2,294	2,330	2,240	—	2,330
Internal Height (mm)	2,393	2,393	2,698	2,550	2,391	2,240	—	2,391
Door Opening Width (mm)	2,340	2,340	2,340	2,290	—	—	—	2,340
Door Opening Height (mm)	2,280	2,280	2,585	2,545	—	—	—	2,280
Volume (CBM)	33.1	67.5	76.0	67.9	32.8	—	21,000-26,000L	32.8
Maximum Payload (kg)	28,200	28,800	28,620	29,500	28,200	40,000	26,000-36,000	28,200
Tare Weight (kg)	2,200	3,700	3,900	4,200	2,400	3,200	3,500-5,000	2,350
Suitable Cargo	General cargo	Light bulky cargo	Light bulky, large-volume cargo	Temperature-controlled cargo	Over-height cargo	Overweight/oversized cargo	Liquid/gas	Organic cargo

Data source: ISO 668:2020 standard + official container type parameter tables from major shipping lines (Maersk/MSC/COSCO). Volume note: The volumes in the table are theoretical maximum values calculated based on internal dimensions. The actual loadable volume is affected by cargo packaging shape, stacking method, and the container's internal structure (corrugated sidewall protrusions), and is usually 10%-15% less than the theoretical value. For practical reference values: see the "Actual Loading Capacity" section under Dimensions and Specifications.

III. Detailed Explanation of Each Container Type

1. Dry Container — The Most Common Container Type

The dry container is the mainstay of the container family, accounting for over 80% of global shipping capacity. Its sealed structure makes it suitable for most general cargo.

Container Type	Common Uses
20GP	Heavy cargo (machinery, hardware, stone, chemicals) — cargo that is small in volume but heavy in weight
40GP	Light bulky cargo (furniture, home appliances, daily necessities) — cargo that is large in volume but relatively light in weight
40HQ	Cargo that requires more height — 305 mm higher than 40GP, providing about 13% more volume
45HQ	A common solution for light bulky cargo — 1.5 m longer than 40HQ, with 15% more volume capacity

Key Points of the Internal Structure of Dry Containers:

The floor is mostly made of hardwood (APG/MDG plywood), with a load capacity of about 3–4 tons per axle
There are corner castings at the four inner corners, used for securing and stacking
The side walls have corrugated steel plates to increase structural strength
There are locking bars on the inside of the container doors; after loading, they are locked and sealed

2. Reefer Container — Dedicated to Temperature-Controlled Cargo

Reefer containers have a built-in refrigeration unit and can maintain the internal temperature at any set value between -30°C and +30°C.

Feature	Description
Cooling Method	Electric cooling (connected to ship power 440V/60Hz)
Temperature Range	Settable from -30°C to +30°C
Temperature Holding Time	Maintains temperature for 8–12 hours after power failure (depending on outside temperature)
PTI Inspection	Pre-Trip Inspection is required before each loading
Applicable Cargo	Frozen food, seafood, fruit, pharmaceuticals, flowers

In addition to basic freight, reefer containers also require electricity charges and temperature-control-related fees; the specific items and billing methods are subject to confirmation by the shipping company.

3. Open Top Container — Dedicated to Overheight Cargo

Open top containers use a waterproof canvas instead of a steel roof, allowing cargo to be loaded and unloaded from above.

Feature	Description
Greatest Advantage	Can load cargo taller than the standard container door (up to 2.4 m in height)
Top Cover	Waterproof canvas secured with lashing ropes
Loading/Unloading Method	Loaded/unloaded from the top by crane/forklift
Height Limit	The top of the cargo must be ≤30 cm from the top frame of the container

Applicable Cargo: Large mechanical equipment, glass, steel structures, marble, timber, extra-long pipes.

4. Flat Rack Container — Dedicated to Overweight and Oversized Cargo

Flat rack containers have no side walls or roof, only a floor and two ends, and can be loaded and unloaded from any direction.

Feature	Description
Maximum Payload	20FR can reach 40,000 kg (1.5 times that of a dry container)
Collapsible	Both ends can be folded, saving space when empty containers are returned
Loading/Unloading Method	Crane can load/unload from above/front/side

Applicable Cargo: Engineering vehicles, generator sets, large castings, marine spare parts, steel coils.

5. ISO Tank Container — Dedicated to Liquid Cargo

An ISO Tank is a stainless steel tank mounted within a standard container frame, used for the safe transport of liquids and gases.

Parameter	Standard 20-foot tank container
Capacity	21,000–26,000 L (depending on liquid specific gravity)
Maximum Payload	26,000–36,000 kg
Tank Material	Stainless steel (304/316L, depending on cargo corrosiveness)
Design Pressure	4–10 bar (depending on cargo type)
Applicable Cargo	Chemicals, food oil, alcohol, liquefied gases

Usage Precautions:

When alternating between different cargoes, tank cleaning (CIP cleaning) is required; the cost depends on the cargo type and cleaning requirements
Tank containers for dangerous goods must comply with IMDG Code requirements

6. Ventilated Container — Dedicated to Organic Cargo

Ventilated containers have ventilation openings in the side walls (usually one row at the top and one at the bottom), using natural convection to circulate air inside the container.

Feature	Description
Ventilation Method	Natural ventilation (unpowered), convection through ventilation openings in the container walls
Ventilation Openings	8–12 at the top and bottom respectively, adjustable open/close
Applicable Cargo	Coffee beans, cocoa, onions, garlic, grain, tobacco

Difference from Dry Containers: Dry containers can theoretically also carry organic cargo, but the lack of forced ventilation may cause the cargo to become moldy. Using ventilated containers can greatly reduce the risk of cargo damage and is a common solution for this type of cargo.

7. Garment Container — Dedicated to Clothing

Garment containers are equipped with hanging rods and lashing devices inside, allowing finished garments to be transported while hanging and to be put directly on shelves for sale after arrival at port.

Feature	Description
Internal Height	150–200 mm higher than a standard container
Hanging Rod	Can bear 600–800 kg/m
Capacity	A 40-foot garment container can hang about 1,500–2,000 garments

Applicable Scenarios: Fast-fashion brands, high-end garment exports — saving the cost of ironing and shelving after arrival at port.

8. Car Container / RORO — Dedicated to Vehicle Transport

Car containers (also called flat rack containers or dedicated vehicle containers) are used to transport complete vehicles.

Feature	Description
Loading Method	2 vehicles per layer; a 20-foot container can hold 2 vehicles, and a 40-foot container can hold 4 vehicles
Securing Method	Tire chocks + lashing straps
Applicable Vehicles	Sedans, SUVs, small trucks

IV. Selection Decision Process

What is your cargo?
    │
    ├── General dry cargo (cartons/wooden crates/pallets)
    │   ├── Heavy cargo (>8 tons/20CBM) → 20GP
    │   └── Light bulky cargo (<8 tons/20CBM) → 40GP or 40HQ
    │
    ├── Requires temperature control (frozen/chilled/insulated)
    │   └── → Reefer container (Reefer)
    │
    ├── Over-height / over-width / over-length
    │   ├── Over-height (>2.4m) → Open-top container
    │   └── Overweight or oversized cargo → Flat rack container
    │
    ├── Liquid/gas
    │   └── → Tank container (ISO Tank)
    │
    ├── Organic/mold-prone
    │   └── → Ventilated container
    │
    ├── Garments/apparel
    │   └── → Hanging garment container
    │
    └── Vehicle transport
        └── → Car container

Quick Selection Mnemonic

Heavy cargo: 20GP; light cargo: 40HQ; temperature control: reefer; over-height: open-top; overweight: flat rack; liquids: tank container; organic cargo: ventilated; garments: hanging garment container.

V. Pre-selection Checklist

□ Single-piece dimensions: Does it exceed the container door dimensions (20GP container door: 2,340 mm wide × 2,280 mm high)
□ Single-piece weight: Does it exceed the concentrated load on the container floor (approx. 4 tons over a 500 mm × 500 mm area)
□ Total weight: Is it subject to road weight limits in the destination country?
□ Height: For single pieces over 2.4 m, consider an open-top container; also consider open-top if cargo cannot be loaded directly through the door
□ Temperature: Cargo requiring temperature control can only use reefer containers; confirm whether the route provides reefer plugs
□ Liquids/gases: Use tank containers; confirm tank material and cleaning requirements in advance
□ Respiring cargo (coffee beans, grain, etc.): ventilated containers are better than dry containers
□ Garments: hanging garment containers can eliminate the need for ironing and shelving at the destination port
□ Overweight/oversized cargo: flat rack containers; apply to the shipping company in advance and confirm the lashing plan
□ Out-of-the-way ports and inland points: first confirm whether the port has a supply of the corresponding container type

Frequently Asked Questions

Can dry containers carry all general cargo?

Most can. Pay attention to respiring or moisture-prone cargo—dry containers do not have forced ventilation, and condensation can easily form inside during long voyages. Such cargo is better suited to ventilated containers, or add desiccants and proper lining inside the container.

Can reefer containers be used directly as dry containers?

Technically yes, but reefer container supply is relatively tight and the cost structure is different, so it is generally not recommended. The value of a reefer container lies in temperature control; occupying a reefer plug without controlling temperature only adds unnecessary items.

Encyclopedia of Container Types: Parameter Comparison and Selection Guide for 8 Common Container Types