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Postal Encyclopedia

High Density

HD

Mail Classes & RatesUpdated 2026-07-24

A carrier-route price level requiring at least 125 pieces on a single carrier route. Routes a few pieces short pay a higher price on every piece.

Definition reviewed 2026-07-24. This is a plain-English Plavidian reference; for USPS terms, the Domestic Mail Manual is the authority. For your own job, the final mail class, postage, and preparation are confirmed after list processing and production review.

Related terms in Mail Classes & Rates

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