Open top vs flat rack vs platform containers

Open tops keep the size of a dry box and lose about 985 kg of payload to their removable roof, while flat racks and platforms trade walls for strength. The 40ft high cube flat rack has the highest payload of any container on PalletSpec, 47,300 kg, and the 40ft platform the heaviest tare at 5,700 kg.

By Oliver Bennett · Published 29 October 2026 · Data as of 27 October 2026, from spec sheets retrieved that day

When cargo is too tall, too wide or too heavy for a closed box, three kinds of container take over. An open top is a dry box whose roof is a removable tarpaulin, so cargo can be lowered in by crane. A flat rack is a floor with two end walls and no sides or roof. A platform drops the end walls as well and is simply a strong deck with corner fittings.

The 8 types in the data

Open tops: dry boxes without a roof

An open top keeps the dimensions of the dry box almost exactly. The 40ft open top gives up only 1.3 m³ of volume against the standard 40ft, and every one of the 11 pallet standards keeps the same floor count. What it loses is weight: the box is 170 kg heavier, and its typical payload is 985 kg lower. At 26,615 kg, the 40ft open top has the lowest payload of the special types here.

The roof opening is smaller than the floor, and its size varies a lot between sheets; the figures are in container door dimensions. A high cube open top adds height for loads that stand proud of a standard box: its typical inside height is 2,653 mm.

Flat racks: built for weight

Flat racks carry far more than any closed box. The 40ft high cube flat rack has the highest payload of all 16 types on PalletSpec, 47,300 kg on a gross rating of 52,500 kg, though only one source publishes it. The ordinary 40ft flat rack carries 40,000 kg. These are boxes for steel coils, machinery and vehicles, cargo that reaches its weight limit with most of the space empty.

Their dimensions are the least standard in the data. Usable width in the 40ft flat rack runs from 2,116 mm to 2,400 mm across three sources, and the 20ft flat rack's payload from 30,140 kg to 35,000 kg. Some designs have fixed end walls, some fold flat, and corner posts differ. Width and height figures are the space between posts and above the deck, but cargo on a flat rack can stand out past both, which is the point of using one.

Platforms: just the deck

Platforms publish their outside size only, since there are no walls to measure inside: 6,060 mm by 2,440 mm for the 20ft and 12,190 mm by 2,435 mm for the 40ft. The 40ft platform has the heaviest tare of all 16 types, 5,700 kg, and carries 39,300 kg. The 20ft platform weighs 2,630 kg and carries 29,610 kg.

Payload per kilogram of tare

Ranked by payload per kilogram of tare, the short boxes come first among these eight types: the 20ft open top leads with 12.61, then the 20ft flat rack at 11.93 and the 20ft platform at 11.26. Among the 40ft types the 40ft high cube flat rack does best with 9.10. The 40ft open tops sit near the bottom: they share the dry boxes' gross ratings while weighing more empty.

Which one to ask for

The choice follows the cargo. If it fits inside a dry box but has to be craned in, an open top keeps it covered and keeps the pallet counts of a dry box. If it is wider than the walls or taller than an open top allows, a flat rack is the usual answer, with the end walls to secure against. Platforms suit very long or very wide pieces that need nothing but a strong deck. Flat racks, platforms and tanks have no fixed floor to plan pallets on, so the load planner leaves them out.

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