I just drill holes into cardboard and insert the chips. This makes them the same thickness as the cardboard in a regular envelope and I can send them through and pay the extra .17 cents and let them go as "rigid" and have them hand stamped so that they do not go through the sorting machines. I do insert and extra shirt cardboard in front to make sure they don't get pushed out. Just make sure it is not more than 1/4" thick.