The Swagman Semi 4. 0 2 Bike Add-On is designed to expand the capacity of the Semi 4. 0 hitch rack from 2 bikes to 4. Like it's parent rack, it fits mountain or road bikes with 20 - 29in wheels, as long as each bike doesn't exceed 45lb. The ratchet arms secure your bike to the rack without making any contact with the frame, and will lock your bike to the rack with the included cable lock. Rear wheel ratchet straps hold your wheel firmly without scratching it thanks to the padded bumpers. Please note this is not a standalone rack, it must be used in conjunction with the Semi 4. 0 2 Bike Locking Bike Rack.