Not every shipment can get by with a basic poly mailer. If you're shipping circuit boards, precision metal parts, or defense-contract goods, the shipping bag you choose directly affects whether that product arrives usable. This guide compares the main types of shipping bags, from everyday poly mailers to MIL-SPEC barrier bags, so you can match protection level to what you're actually shipping.
Why the Right Shipping Bag Matters
For low-value, non-sensitive goods, a standard mailer is usually fine. But for electronics, metal components, or contract-mandated shipments, the wrong bag can mean static damage, corrosion, failed inspections, or a rejected delivery. The right bag protects the product, controls cost by avoiding over-packaging, and, for defense and aerospace shipments, keeps you compliant with the specification your contract requires.
Types of Shipping Bags
Here's how the main categories compare:
|
Type |
Protection Level |
Best For |
|
Poly mailers |
Basic, water-resistant only |
Non-sensitive, low-value goods |
|
Bubble-lined mailers |
Cushioning against impact |
Small parts that need shock protection, not moisture protection |
|
Antistatic / ESD shielding bags |
Static discharge protection |
Circuit boards, semiconductors, electronic assemblies |
|
Moisture / foil barrier bags |
Moisture and vapor barrier |
Corrosion-prone metal parts, humidity-sensitive goods |
|
MIL-SPEC barrier bags |
Highest: moisture, vapor, and often static protection to military spec |
Defense, aerospace, and industrial goods requiring compliance |
For a deeper look at moisture protection specifically, see our guide to different types of moisture barrier bags, and for static-sensitive goods, see our overview of static shielding bags.
Protecting Sensitive and High-Value Shipments
Standard mailers and bubble-lined bags handle physical bumps, but they don't address the two failure modes that matter most for sensitive goods: static discharge and moisture.
Electronic components need MIL-PRF-81705 static shielding bags to prevent electrostatic discharge from damaging circuit boards and semiconductors during transit.
Metal parts and moisture-sensitive goods need MIL-PRF-131 barrier bags paired with desiccants to control humidity and prevent corrosion inside the package.
Where a sealed barrier is required, heat-sealable MIL-DTL-117 barrier bags create a true moisture and vapor barrier rather than just a water-resistant layer.
Shipping electronics, metal parts, or defense goods? Royco stocks ESD, moisture barrier, and MIL-SPEC shipping bags ready to ship.
How to Choose a Shipping Bag
Work through four questions: How sensitive is the product to static, moisture, or corrosion? How long and under what conditions will it be in transit? Does the bag need to be heat sealed for a true barrier, or is a standard closure enough? And does your contract or industry require a specific MIL-SPEC? Answering these narrows the choice quickly. A poly mailer is fine for a T-shirt; it is not fine for a circuit board or a machined part headed overseas.
When You Need More Than a Mailer
Basic poly bags are built for convenience and low cost, not protection. Barrier bags, whether moisture, static, or MIL-SPEC rated, are engineered to control a specific risk. If your shipment has any real sensitivity to humidity, static, or corrosion, or if it's headed for export or a defense contract, a barrier bag is the right category to start from. Our export packaging resources cover the broader compliance picture if you're shipping internationally.