i find parking cards i quite hard you don't know how. with cards you have to be carefull so they don't get scratched or bent.
my tips follow.
.always seal your nveope tight with tape so it can't open
.always plas the cards in slips so they cannot be scratched
.always place the cards between two pieces of card board so the package cannot bend.
.make sure cards are all on top of each other to prevent falling through the sides of the card board
.always take care in posting and placing your cards in the mailbox.
cheers, i hope this can help you.