The revised key holder makes the Nuki Smart Lock 2.0 compatible with common knob cylinders. The adapter serves as a connection piece between the knob cylinder and your Smart Lock 2.0. In the next step, select the manufacturer of your cylinder so that the appropriate adapter for your knob cylinder can be added. You can often find the manufacturer of the cylinder (for example, EVVA, CISA, KESO, etc.) on the outside of your door. The illustrated matrix provides an overview of the shape your adapter can have.