Question 1

What is a cluster box unit?

Accepted Answer

A cluster box unit (CBU) is a freestanding, multi-compartment outdoor mailbox that consolidates mail delivery for many addresses at a single centralized location. Each tenant has a private locking door, and shared parcel lockers hold packages. CBUs serve neighborhoods, HOAs, apartment communities, and new developments under the USPS centralized delivery model.

Question 2

Do cluster box units have to be USPS approved?

Accepted Answer

Yes. For the Postal Service to deliver to and master-key a unit, the cluster box unit must be USPS approved and meet the USPS-STD-4C specification. Approved CBUs use a master Arrow Lock housing for carrier access and individual tenant locks, and only approved units may be installed on new centralized delivery routes.

Question 3

What door sizes do cluster box units come in?

Accepted Answer

Standard USPS-approved cluster box units are offered in 8, 12, 13, and 16 tenant-door configurations. Most 12, 13, and 16 door units include one or two integrated parcel lockers for package delivery, and units can be ganged together to serve larger communities.

Question 4

Who is responsible for buying and installing cluster box units?

Accepted Answer

The cost of purchasing and installing CBUs is the responsibility of the property developer or HOA. Developers must coordinate with the local USPS Growth Manager during planning, propose CBU locations on the site plan for USPS approval, and meet ADA accessibility requirements before delivery can begin.

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