The Master Lock No. 4400D Bluetooth® Padlock features a 1-29/32in (47mm) wide metal body for durability. The 9/32in (7mm) diameter shackle offers 7/8in (22mm) 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. The 1 Year Limited Warranty provides peace of mind from a brand you can trust.