Our size chart (How to Choose Dunnage Bag Sizes) answers “which dimensions fit which void.” But picking the right dunnage bag for container shipping is not a one-look decision — it is a workflow: measure the void, match the performance level, choose the pressure rating and material for your cargo and transport mode, select the valve, and trial before ordering in bulk. Follow the five steps below and you will rarely end up with the wrong bag.

Step 1: Measure the Void the Right Way

A bag sized from a guessed void is a gamble. Measure after loading is finished, when cargo sits in its final position:

• Use a tape to measure the void width at several points along the container length — voids are rarely perfectly even; work with the widest measurement you find.
• Also measure the cargo stacking height; bag height should match it or sit slightly lower, leaving a little working room at the top.
• Remember that voids “breathe”: cargo can settle slightly during ocean transit, and temperature changes affect air pressure. If your measured void sits between two standard sizes, choose the larger bag and run it at a moderate pressure rather than forcing a small bag to stretch.

Step 2: Match the AAR Performance Level to the Void

The industry uses the AAR (Association of American Railroads) level system as a reference framework for dunnage bag performance. Levels 1–5 correspond to the void width the bag is tested against — roughly:

• Level 1: voids up to about 18 inches
• Level 2: voids up to about 12 inches
• Level 3: voids up to about 8 inches
• Level 4: voids up to about 6 inches
• Level 5: voids up to about 4 inches

The rule of thumb: the larger the void and the heavier the cargo, the higher the level you should aim for. A small void with light cartons needs only a lower level; a wide void between heavy pallets needs a higher-rated bag. Note that this level system is a performance classification — actual AAR certification is a separate railroad compliance process (see our note on certifications below).

Step 3: Select Pressure Rating and Material by Cargo Weight and Transport Mode

With the level set, decide how “strong” the bag itself must be:

• Cargo weight: heavy machinery and dense pallet loads need thicker, higher-rated material; light consumer goods do fine with standard specifications.
• Transport mode: ocean containers see rolling, pitching and long voyages — choose material with good abrasion resistance. Rail and intermodal transport adds harsher longitudinal shocks, so go one level up or select the higher-rated option when rail is involved.
• Material choice: kraft composite bags are abrasion-resistant and easy to handle; PP woven bags handle humid ocean conditions well. Match material to your route, not just your cargo.

Never exceed the bag’s rated working pressure — see our guide on dunnage bag inflation pressure for safe inflation practice.

Step 4: Pick the Valve Type

The valve decides how fast — and how easily — your team can inflate the bags:

• Standard valves work with the usual setup: air compressor + inflation gun + pressure gauge. Fine for moderate daily volumes.
• Large valves inflate noticeably faster and seal automatically, which pays off when your team loads many containers per day.

Whichever you choose, confirm your inflation equipment fits the valve before ordering — a mismatch at loading time is an avoidable headache.

Step 5: Trial With Samples Before Bulk Ordering

Before committing to volume, order samples and test in one real container with your actual cargo. Check the securing result on arrival: no shifted pallets, no burst or abraded bags, valves intact. A single trial run confirms size, material and valve choice far better than any specification sheet.

For planning purposes: Tezheng’s export MOQ for dunnage bags is 5,000 pcs, and lead time is about 20 days from production to port (production-to-port; ocean freight time is additional). Our SGS test report for dunnage bags covers chemical safety under the US TPCH toxics-in-packaging legislation — it is a chemical compliance report, not a railroad performance certification such as AAR.

Frequently Asked Questions

What is the AAR dunnage bag level system?

It is an industry testing framework from the Association of American Railroads that classifies dunnage bag performance into Levels 1–5 based on the void being bridged: Level 1 covers up to about 18 inches, Level 2 about 12 inches, Level 3 about 8 inches, Level 4 about 6 inches, and Level 5 about 4 inches. Heavier cargo and larger voids call for a higher level.

Should I choose the dunnage bag by void width or cargo weight?

Start with void width — it decides the bag dimensions. Then adjust the pressure rating and material by cargo weight and transport mode: heavier cargo and rail/intermodal transport call for higher-rated, thicker material, while lighter pallet cargo on ocean routes works fine with standard specifications.

What valve type should I choose for dunnage bags?

Standard valves fit the usual air compressor + inflation gun setup. Large valves inflate faster and are better for operations loading many containers per day, since they cut inflation time and seal automatically. Confirm that your inflation equipment matches the valve before ordering.

Should I trial dunnage bags before placing a bulk order?

Yes — order samples first, install them in one real container with your actual cargo, and check the securing result after transport. Tezheng’s export MOQ is 5,000 pcs for dunnage bags, with a lead time of about 20 days from production to port.

Related reading: start with the dimension chart in How to Choose Dunnage Bag Sizes, then check Dunnage Bag Inflation Pressure for safe operating pressures.