The Master Lock No. 4400D Bluetooth Smart Padlock features a 2 inch (51 millimeter) wide metal body for durability. The 9/32 inch (7millimeter) diameter shackle offers 7/8 inch (22millimeter) vertical clearance and is made of boron, offering maximum resistance to cutting and sawing. The smartphone/app interface offers speed, ease of use, and greater control with the ability to share access; with keyless convenience. The locking mechanism features anti-shim technology, offering maximum security. The 1 Year Limited Warranty provides peace of mind from a brand you can trust.