The Master Lock No. 4401DLH Bluetooth Padlock features a 2-7/32in (56mm) wide metal body for durability. The 11/32in (9mm) diameter shackle offers 2in (51mm) vertical clearance and is made of boron alloy, offering maximum resistance to cutting and sawing. The smartphone/app interface offers speed, ease of use, & greater control with the ability to share access, with keyless convenience. The locking mechanism features anti-shim technology, offering maximum security.