Qualarc LIB-AC-LM6-46 Liberty Rear Access Locking Mailbox with 4" to 6" Chute & Antique Copper Letter Plate Mount in masonry walls and columns chute adjusts to match the thickness of your wall Castings are made in solid aluminum and top quality black enamel finish. Manufactured in England Large capacity, secure mail storage with rear lockable door supplied with 2 keys Rear access door opening: 7" w x 7.5" h incoming opening dimensions: 9"w x 2.5" h overall product dimension: h 16.5" x w 11.5" x d 14" weight 18 lbs. Optional anti-theft high security plate can be added to decrease opening front slot to 9" x 1" order item # hs-plate