My post office has been accepting my bubble mailers for at least two years. However, the sender must indicate at the time of mailing that the rate wanted is "First Class, Large Envelope," or it will drop into a different shipping rate automatically. Perhaps, one thing to note, is there is a thickness requirement -- along with flexibility -- as the finished envelope can not be more than a certain thickness. I have been mailing one chip for less than a $1 each and use a corrugated, hot coffee cup holder as my security blanket -- placing the chip between the collapsed cup holder and using my stapler or tape to secure the chip around the cup holder so it won't come out in shipment. I have noticed that other shippers are paying upward to $3.50 and $3.75 to mail one chip. Here's the catch, my post office will let me send the large envelop, first class but that rate does not have delivery confirmation. But, when you individualize an envelope, and attached the extended zip code with makes the item direct deliver like (39520-2189) identifier, they print out a receipt that shows an item went to say Detroit, Michigan and it only shows that the item was mailed. Also, I have a label program that takes the street address, town and state and searches for the extension as shown above. You can add delivery confirmation but must use priority mail handling.
Concerning the hot cup holders you can pick up at most coffee bars -- each hold two chips.
Hope this helps.