Bikes need to be properly balanced on bike carriers. Strap On carriers in particular must not be twisted by unevenly balanced bikes. Use this articial cross bar to solve the problem. It's essential for many ladies bikes, and increasingly required for modern mountain bikes with non-standard frames which are too narrow to hook over the two arms of most 'hang on' and 'strap on' bike carriers. Attaches between the seat and handlebar posts, and telescopes between 400mm and 800mm.