USPS Retail Ground® is ground delivery service primarily intended for single-piece mailings which consist of any mailable matter that is not required to be mailed as First-Class Mail®. There are no bulk prices for USPS Retail Ground. USPS Retail Ground is generally presented at a USPS retail service counter where USPS Tracking service can be initiated. USPS Retail Ground prices are based on the zone (distance) to which the parcel is addressed and the weight of the parcel. While any mailable matter not required to be mailed as First-Class Mail is permitted to Zones 5-8, Zones 1-4 items are limited to mailable hazardous materials, live animals, and other "surface-only" items.