This secret fingerprint doorknob that can unlock with a Bluetooth device (via an app on your smartphone) is a really great product/invention but it’s not perfect (AAA batteries are needed but are not included). It’s bigger than average and slightly adjustable, pretty simple to install on most doors, just don’t forget to connect the wire. If your on the inside far away from the doorknob’s position, it won’t unlock via smartphone for an unauthorized person. You’ll have to manually open it or stand about a foot next to the doorknob in order for it to work. From the lock side, it does come with a set of keys (2) incase and it works very well via smartphone unlock but sometimes it won’t read your fingerprint properly especially if anyone has big/oily/cracked fingers so you will have to try until it opens. There is also a usb type-C charging port hidden below in case if the batteries die so it’s best to keep a charger/power bank handy (haven’t tried it yet).