Roof rack adapter for a fourth bicycle for the Aroso Main roof rack. It increases the capacity of a roof rack by one bicycle. The adapter is mounted with brackets above the wheel rack lamps and extends the length of the rack. Includes a lockable arm that is connected to the frame of the fourth wheel to the rack tray. Includes everything you need for quick and easy assembly. Maximum carrying capacity for 4 bicycles is 60kg. The frame mounting bar fits bicycle frames with a diameter of 20-80mm without a problem.