Periodically, I will have to mail something out that needs protection, such as a CD or photographs. EcoLite Bubble Mailers are an economical way to do this.
Any office supply store should carry these mailers, as well as places such as Walmart. They come in various sizes and prices, and the protective bubble lining inside the mailer is what makes it stronger and safer to use for mailing small items that do not require a box.
My husband has used these mailers to mail important documents of a certain thickness that a regular envelope would not be suitable for. The mailers seal very nicely as well, with a strip that you pull off to expose the adhesive. Upon closure, the seal is tight.
I really enjoy using bubble mailers, and EcoLite has proven to be a reliable brand. They can even be bought by the case, but I don't buy them that way because I don't need that many at one time.
One other thing to remember, if it can fit into a bubble mailer, that's the way to go, because it saves on postage.