Fort Knox Mailbox M1-LT M1-LT Mailbox Fort Knox M1-LT Black Mailbox 38 LBS! (Mailbox Only) Mailbox Size: 10.25"x10"x20" 1/8 in. Thick steel shell (11 gauge) and 1/8 in. Thick steel doors. Incoming mail slot 1 3/4" x 10" All hand welded design. (No spot welds or rivets). NOTE: No Hardware included