4 x Atera GIRO AF+ aluminium bike carriers with roof bars.
Thule HangOn 9708 4 Bikes Towbar Mount Bike Rack | DriveDen
Thule+939+Velospace+XT+4+Bike+Cycle+Carrier+Rack+Towbar+Mount+%7C+Inc+4th+Adapter for sale online | eBay
Thule Apex XT Hanging Hitch Bike Rack, Carries 4 Bikes, Perfect for Traveling with Multiple Bikes - Quick, Tool-Free Installation, Suitable for a Wide Variety of Bike Sizes and Frame Styles :