A mailpiece larger than letter dimensions that remains flexible and meets USPS flat-size standards.
Flat
Large envelope/catalog-sized mail
Preparation & Production
Definition reviewed 2026-07-24. Plavidian reference, written from the USPS Domestic Mail Manual. Final mail classification, postage, and preparation are confirmed after list processing and production review.
Need this applied to a real job?
Ask the Plavidian Mail Expert™ for an answer grounded in the USPS Domestic Mail Manual, or send us the job and we will confirm the preparation before you print.