Which shipping service must be used for packages exceeding 108 inches in length?

The correct option is indeed USPS Retail Ground. This shipping service is specifically designed for packages that are heavier and larger, making it suitable for items that exceed the standard size limits set by other services.

USPS Retail Ground is the most economical option for heavy and oversized packages that do not qualify for Priority Mail or other expedited services. It allows for items up to 130 inches in combined length and girth, which encompasses packages that exceed the 108-inch limit mentioned in the question.

In contrast, other services like Priority Mail Express, First-Class Package Service, and Parcel Select have their own size limitations. For example, Priority Mail Express is primarily for faster deliveries but has a maximum length and girth restriction that is more stringent than that of Retail Ground. First-Class Package Service is intended for lightweight packages and has strict size limits, typically not accommodating larger shipping needs. Parcel Select, while capable of handling heavier packages, also has its own dimensional restrictions that may not include those larger than 108 inches in length.

Understanding these distinctions is crucial for selecting the appropriate shipping method based on the size and weight of the package.