Allen Sports 552QR is a bike rack designed to be used on 2" receiver hitches professionally installed on automobiles. It can carry up to 4 bikes, with the heaviest bikes loaded first and lighter bikes on the outside. The rack is secured to the vehicle using a locking knob that tightens a hitch insert wedge, and a hitch spring pin that engages a hole in the vehicle receiver hitch. The carry arms can be folded up when not in use, and a wire retainer must be fully closed to keep the carry arms in an upright position during use.