Priority Mail Forever Prepaid Flat Rate Envelope

USPS

Brand (USPS) matches exactly, Model ('Flat Rate Envelope') matches the product details, Visual design (white with red borders, 'PRIORITY MAIL' text, USPS logo) is identical to the visible elements in the source frame, Color scheme matches, Overall form factor and dimensions are consistent with a standard flat rate envelope, Retailer (USPS) is an official source, adding to confidence