PLEASE NOTE : These are available for the small/medium/large USPS flate-rate boxes only.
Don't want to leave the house to buy postage for your flat-rate USPS box? We've got you covered.
Once purchased, you'll be emailed the mailer.
You can order USPS flat-rate boxes online for free here : https://store.usps.com/store/results/shipping-supplies/_/N-7d0v8v