letter size papers in a 9x12 envelope might present 'floppy corners that fold over and technically violate the corner radius requirement. In practice USPS doesn't seem to care (although they might if a commercial mailing with 100's or 1000's of pieces - assume it has to do with machinability). The FC Flat max 0.125' corner radius criterion might be tough to satisfy if shoving letter sized papers into an envelope. But maybe the hassle of rounding up an appropriate FC envelope was worth the extra $5 (although you do get tracking with Priority) You actually could have sent it as a First Class Mail Flat with $1.90 in stamps in a manilla, or some sort of non-Priority envelope as it (meets the requirements for a flat: size, < 3/4', uniform, and flexible. flexibility, etc criteria don't apply at all to Priority. What would be the correct Package Type to choose if printing a label for the Tyvek envelope with no extra stuffing in it? I eventually went with the USPS FRPE instead, for $7.55.Īs nobody said, if not PM flat rate, it's a package and ships at regular by weight zoned Priority Rates in PM or user supplied packaging, and the First Class Mail 1/4', 3/4', size. It didn't seem to qualify as a Package/Thick Envelope as it was just a folder of paperwork, and in hindsight I guess I could have stuffed some bubblewrap in there to pad it out, but that doesn't seem like it should be necessary. This was not an eBay sale, so I was looking at options under either PayPal/ShipNow or USPS Click 'n' Ship, but nothing seemed to fit.

It was probably no thicker than a half inch at most, and shipping weight was just 7 ounces (which is why I wasn't looking to spend extra money on their Flat Rate Padded Envelope). I had a manila folder of eBay paperwork to mail to my CPA, and it all fit in the Tyvek USPS Priority Mail envelope (EP14, with a barcode ending in 013). I ran into this problem last night, and finally worked around it by using the USPS FR Padded Envelope instead, but I'd still like to find an answer for next time.

Usps flat rate tyvek envelope