If you have an online business, you would need to pack and ship all sold items. It would help if you know which packing material to use efficiently. Having this knowledge and expertise allows you to save and therefore increase income as well.
For instance, boxes are quite versatile because you can use them for small and large items. They can also be sturdy and quite durable. However, an envelope would come out cheaper because it is small and it is light. So you are only shipping some stickers, stamps or even small accessories, you can use envelopes to save on postage. Just make sure that you protect the items with plastic bag and bubble wrap. The ordinary envelopes can easily get torn. And so to protect the item you should get a thicker envelope.
If you are shipping books and CDs, you should even get a padded envelope. Medicines and electric items are even more protected by bubble wraps. This would make them safer against heat and shock.
But if you are shipping fabric and other clothing materials, you need to make sure it will not get soiled. For this purpose, you should use the polymailers. With its plastic-like construction it would surely provide appropriate protection. You don't have to pay extra for the postage. Although you will pay for quality envelopes, it would still be worth it.