These are the most common, and generally the cheapest way to carry up to four bikes. The carriers use the tow ball as a big nut and bolt to hold them on to the towbar. If you have a towball that cannot be removed from the towbar you'll need a carrier from our Towball Mounted Bike Carriers page. If your towbar is a removable square tube, you can also use carriers from our Receiver Hitch Mounted Bike Carriers page.