About this itemLarger inner compartment can accept a USPS priority mail large flat rate box 12 in. x 12 in. x 5.5 in. and still has room for additional mail and parcelsHeavy gauge galvanized steel body equipped with stainless steel door pins then fully powder coated for corrosion resistanceSleek magnetic door closure provides reliability all while keeping door firmly closedPredrilled 4 in. x 10 in. hole pattern in floor allows for mounting to existing post (installation hardware not included)Order Architectural Mailboxes adapter plate 7540B for 4 x 4 wood post installationOverall dimensions: 14 in. W x 12 in. H x 18.3 in. DApproved by the US postmaster generalWorks with Architectural Mailboxes post models 5526, 5525, 7516, and 7507