A Key Keeper stores the building's key for the carrier to access the building. Each Key Keeper is prepped to house the USPS lock. This version is made of heavy gauge US32D brushed stainless steel and is designed for recessed mount only. Painted finishes available upon request. Exterior dimensions: 3-1/4" high x 6" wide x 1-15/16" deep. Rough opening dimensions: 2-1/2" high x 5" wide x 1-3/4" deep.