The simple difference
A poly mailer is usually a flexible outer bag for soft or already-protected goods. A bubble mailer adds cushioning for small items that need more protection than a plain bag but not always a full box.
Decision table
| Product type | Possible choice | Why |
|---|---|---|
| T-shirt or soft clothing | Poly mailer | Light, flexible, and weather-resistant. |
| Small accessory | Bubble mailer or box | Depends on crush risk and value. |
| Book or paper item | Rigid mailer or box | Bending and moisture matter. |
| Fragile item | Box with cushioning | Flexible mailers may not protect enough. |
Cost and perception
A mailer may lower weight and size, but the package still needs to look appropriate for the product. A poorly protected order can cost more through refunds and poor reviews.