The Master Lock 5400D Portable Lock Box features a 3-1/4in (83mm) wide metal body for durability. The portable design offers removable "over the knob" installation. Set your own 4-digit combination for keyless convenience and increased security. The shutter door protects combination dials from weather, dirt and grime; and molded body and vinyl coated shackle prevent scratching. The Limited Lifetime Warranty provides peace of mind from a brand you can trust.