This is a system by THULE that allows you to unify the keys used for their base carriers, attachments, and roof boxes. By replacing the key cylinders, you can operate multiple carriers with the same key. Includes: * 3 Master Keys * 7 Key Cylinders * 1 Blank Key for Cylinder Replacement There were originally 8 key cylinders when purchased, but one has been lost. Everything in the photos is included. Instruction manual not included; please search online. This is a used item, so please refrain from purchasing if you are overly concerned about condition.