The Super Letter Satchel is the ultimate letter storage unit—essentially, it's four boxes in one. The bottom section features 16 large compartments (2⅞″ x 3⅛″). The two side boxes each have 15 compartments (2¼″ x 1⅛″). The top section has 42 compartments (1¼″ x 2¼″), plus several additional storage areas.