Which class of mail includes parcels with any dimension less than specified?

The class of mail that includes parcels with any dimension less than specified is First-Class mail. This category is designed for sending letters, postcards, and parcels that meet certain weight and size criteria. First-Class mail is typically prioritized for speed and reliability, making it a common choice for essential communications and parcels that require timely delivery.

Parcels sent via First-Class mail can weigh up to 13 ounces, and it accommodates packages with dimensions that may be less than the maximum specified size. This flexibility allows individuals and businesses to send smaller parcels efficiently without needing to upgrade to a higher service tier, like Priority Mail, which has stricter size and weight limits.

The other classes of mail, such as Marketing Mail, Package Services, and Periodicals, are intended for different types of content delivery and may have their own specific requirements regarding dimensions, weight, and purpose. Marketing Mail is primarily used for bulk mailings, Package Services encompasses a range of shipping options for packages often larger than what First-Class allows, and Periodicals are for publications and newsletters that meet specific criteria for distribution.