The Master Lock Bluetooth® Indoor Padlock features a 47mm wide metal body for durability. Its boron alloy shackle offers maximum resistance to cutting and sawing. Use your smart phone to open and manage your lock via the Master Lock Vault Enterprise app (apple and android). No keys to lose, no combinations to forget. No unauthorised key duplication. These locks can withstand physical attacks and hacks, protecting your property with military grade encryption and high-security features. It also features backup access, ideal if your phone runs out of battery, using a directional code on the lock keypad. There is also a low battery notification/reminder via the padlock and in app. Specifications: Body Width: 47mm.Shackle Diameter: 7mm.Shackle Height: 22mm.Shackle Width: 21mm.