USPS provides shippers with boxes for Priority Mail, however, your own personal boxes may be used as well.
If you choose Priority Mail using your own packaging, the maximum combined length and girth (the thickest part of the package) is 108". Learn how to measure your packaging.
Priority mail is charged by weight only, so as long as your package conforms to these dimension restrictions, and is under 70 lbs. your package should send properly.