The Master Lock No. 5441EC Bluetooth® Wall Mount Lock Box features a 3-1/4" (83mm) wide metal body for durability. Secure your home or business with the Master Lock Vault System for unmatched security, simplicity and accountability using the latest in Bluetooth lock technology from Master Lock. These locks withstand physical attacks and hacks, protecting your property with military grade encryption and high-security features. Administrators control individual or system-wide lock access with our convenient app and web interface options, while users enjoy simple, secure access to assigned locks or lock boxes.