Flight case: cutouts for standard audio guestbook: 
External Length: 310mm 12 1/4 inches
External Width: 130mm 5 1/8 inches
External Height: 240mm 9 1/2 inches
Internal Length: 300mm 11 3/4 inches
Internal Width: 230mm 9 inches
Internal Inside Case Depth: 85mm 3 3/8 inches
Internal Lid Depth: 35mm 1 3/8 inches