Thank you for viewing. This is a set of two. I purchased these about 10 years ago and used them without any problems. (I left them attached to my car in a covered parking area) By reversing the parts that hold the bicycle, you can load a bicycle from either the right or the left. These are only compatible with aero bars. There are no parts to clamp to square base bars. There are two keys for each, just like when I bought them. There are scratches and dirt from use. Please understand. *Please refer to the THULE website for the instruction manual. If you need any other parts, you can order them from the abe shokai website, which handles Thule products. I will pack them with cushioning material and ship them in a cardboard box. Thank you.