The Motobilt shackle plates are made out of 3/8 inch thick steel plate that is cnc laser cut. Each shackle plate uses 1/2 inch holes and a 3rd middle hole that can be used as a tie plate. A small tube would be cut to length and installed in the middle hole with a 1/2 inch bolt to increase the rigidity in some applications. Measurements are the span from centers on each hole.