The smart lock is made up of metal material, which can be used for a long-term period. The surface is coated with chromium material and it is designed to be anti-skid. With automatic locking retractor, the electronic door will automatically lock behind you after opening for 3 seconds. It is way easy to install and it can quickly be finished just by following the steps of the user manual we provide. In addition, you can set a series of passwords to protect your family members, friends or tenants. The maximum length is up to 10 digits. THREE METHODS OF UNLOCKING: After installing this magical smart lock, there are three ways to unlock the door. High precision fingerprint identification, bid farewell to the traditional unlocking method. Other One is to use passwords powered by AAA batteries to get the door open or you can prefer the traditional way- spare keys to unlock the door. In this way, you won’t be stuck outside your house once the smart lock is out of juice. This keyless smart lock is equipped with a backlight mode, which allows you to clearly see the keyboard in a dark environment. What’s more, it is waterproof and the waterproofing grade reaches to 4 levels. There is a wide range of application of this smart lock and it can be widely used in all kinds of doors of different materials. For instance, wooden door, metal door, glass door and stainless-steel door and so on. It fits the door thickness between 32-48 mm (1.25~1.88 inch).