I use the safe t mailers for up to 3 chips in a #10 envelope. I have a scale so I can weigh any package and put on the correct postage. I also put each chip in a 2x2 plastic flip just so they are not affected by the glue. One thing I do not ship that way is poker chips. They are so brittle that they may break if the PO still runs them thru the sorter (which they do frequently). I ship so many that way that I bought a red ink "Non-machinable" stamper. And yes, you should argue with the PO cage critters. Most of the time they have no idea of what their own rules are. They used to tell me that anything that is not an envelope must be a package (at that $5 plus charge) even though they have a large envelope category. BTW - one thing to watch out for if you use the mailers - squish them down a little or they will be over the 1/4" max thickness allowed for an envelope. Between 1/4" and 3/4" is normally a large envelope and you still have to pay a "rigid" surcharge. I also made my own 1/4" and 3/4" cardboard "guide" to make sure my letter or large envelope is not over the max thickness.