I stock the hinge pin clips as they were also used on the E-Body decklids. They are so small, that hey can go out in a regular mail envelope and traditional postage.
I once shipped 4 small phillips head screws in a basic standard size paper only envelope.
The USPS sorting machine ripped the envelope open. Buyer received a torn and empty envelope. So I learned the hard way, padded/bubble wrap lined envelope at minimum.
These push clips are about the same thickness as dimes. We don't know what the automated sorter can pass. Cheers
