What precautions should I take to send a computer peripheral through the mail?

I want to make a little more money to build a PC by selling unused parts from my current one on eBay. I figured I'd start with the PCI modem, since I don't use dial-up. The modem came preinstalled on the computer, so I don't have any original packaging to put it in. What should I put the modem in the box with to ensure that it doesn't get damaged?|||Depending on the part, make sure you have padding or bubble wrap for all parts and that they are secured. Also get Fragile stickers when mailing. Box would be optimal but an envelope usually works!|||bubble wrap. pci cards will be pretty durable. just about 2 sq feet of bubble wrap and a few pieces of tape.|||static free bag and bubble wrap