Sometimes you can ship an envelope with a chip in it for 37c, Kenny, but postal regs do require that thick envelopes under 1 ounce have 49c postage. You'll find that you get some back for added postage if you start out with only 37 cents.

If what you're using is the corrugated cardboard with adhesive on one side, I used to use this for mailing chips. However, I found there were enough times where there were postage problems, or damage due to USPS cancelling machines that I went to the bubble pack envelopes that most use today. Cost is really not much different and your shipment is safer as they can't put these through the high speed handlers. In fact, about half the time they don't cancel the stamps at all, so if you're careful you can use it a second time free [g].