You are not supposed to send anything but paper in standard envelopes. If a PO clerk bothers to check and feels “something”, they will direct you to ship USPS Ground.

That being said, it makes no sense to sell a $3 chip and charge $6 to ship. So, a couple of options:

* as others have stated, pack it so you can’t feel a chip in it - cardboard filler, etc. Regardless, I always recommend to pay the additional NON-MACHINEABLE option. That “supposedly” guarantees that the envelope will not be put through the PO sorting machines. Doesn’t always work - chips break.

* If shipping USPS Ground, there are a lot of options to print labels online at a discount (Pirate Ship, ShipStation, etc.) Cheaper than USPS prices and you don’t have to wait in line.