Mailing bags and courier bags usually need to meet the following performance requirements:

1. Strength and durability: The bag must have sufficient strength and durability to withstand pressure, tearing or other external forces during transportation. This can be achieved by choosing suitable materials and reinforcing structures.

2. Waterproof and moisture-proof: The packaging bag should have waterproof and moisture-proof properties to protect the contents inside from moisture and moisture. This is especially important for protecting cargo from rain or humidity.

3. Anti-vibration and cushioning: the packaging bag should be able to reduce the impact of external vibration on the internal items. This can be achieved by adding cushioning materials such as foam or bubble wrap to absorb and disperse shock and impact.

4. Size and capacity: The size and capacity of the packaging bag should be selected according to the size and weight of the items contained, so as to ensure that the items can be safely placed and suitable for transportation.

5. Sealing method: The packaging bag should have good sealing performance to prevent the contents from falling or leaking. Common closure methods include self-adhesive closures, heat seals, or zipper closures.

6. Transparency: In some cases, the packaging bag needs to have a certain degree of transparency in order to facilitate the inspection of the contents or identification of the internal items.

7. Reusability: Some packaging bags are designed to be reusable, so they should have sufficient durability and a reliable closure for multiple uses without fraying or damage.

These performance requirements may vary depending on specific packaging needs and shipping methods. Therefore, it is very important to choose the appropriate packaging bag according to your specific situation and needs.