Lock box application: For indoor and outdoor use; large internal cavity allows secure storage for multiple keys Ease of use: Resettable 4 digit combination for keyless convenience, set and reset your combination allowing thousands of personalized combination code options Durable design: Lockable key storage designed to fit over a door knob for portable use; metal body construction for durability and shutter door to protect combination dials from weather Ideal for set of keys: shackle dimensions (refer to visuals) a: 9 mm B: 37 mm C: 48 mm; exterior dimensions (H x W x D) 18.8 cm x 10.5 cm x 4.3 cm; interior dimensions (H x W x D) 10.1 cm x 6.4 cm x 3.