The Bold Smart Lock allows keyless entry & exit in to your home, giving convenience to your whole family. The Bold Smart Lock also allows you to control who can have access to your house. The door can always be unlocked from the inside, which means you can always leave safely during emergencies. This smart lock is easy to install & operate via the Bold app.There are many different sizes of cylinders and the Bold lock is suitable for as many doors as possible. Bold is made for a maximum inside length of 35mm and outside length of 45mm.