You can go on the USPS.com website & when you put in the zipcode your mailing to, you will see the different Priority options. They have added a few Priority boxes of different sizes. I got a flyer in the mail last week advertising the new boxes & you can get a "starter kit" of the different size boxes if you order on their website. My local post office rarely has all the different size boxes, so I order them online & postman brings them to me.