A couple months ago, I took a bubble mailer to the counter at the post office with one chip in it. When the gruntled employee asked me if I wanted any of the additional options available (as she proceeded to verbally go through the memorized list), I told her I'd like 1st class, with delivery confirmation. She said I couldn't do that with a "large envelope" because it wasn't 3/4" thick unless I wanted to ship it Priority Mail. I declined, and then asked her why they had the 3/4" requirement. She looked me straight in the eye and told me, "the Post Office wants to make more money by making you send these by Priority Mail". I thanked her for her honesty!