What we need to keep in mind is that the driving force behind these new rates is the USPS desire to automate everything they can. Ultimately, if it looks like a letter, it will go through a high-speed handler where it will be bent, sorted, stamped with codes, cancelled, and stacked.

This means that even if you are able to meet the letter of the regulation (defining a letter), you must be prepared to have your chips given some pretty rough handling in a machine that expects only uniform sheets of paper. It may be worth the risk if your chip is only valued at a dollar or two, but for better chips, I suggest you ship them so they DO NOT APPEAR TO BE A LETTER. For the extra dollar or so you pay, you get manual treatment and fewer smashed, broken, or lost chips. Think of it as a kind of insurance.

Bubble envelopes will still be the most cost-effective vehicle for most chip shipments if you take into account the potential for damage. For really good chips (say $300+), the Priority Mail Box is a good investment.