Our 2.5 LB Weight Stack Add-on Plate has a thick coating of virgin rubber to protect the finish of the weight stack. Will not mar the surface of your weight stack guide rods. You may use this add-on plate with other 2.5 LB or 5 LB add-on plates in any combination to get 2.5, 5, and 7.5 LB increments. Each add-on plate has molded male and female detents that interlock when stacked, thus preventing them from sliding around during exercise. Carry these in your workout bag at the gym and use it anytime you need to progress in 2.5 LB increments instead of 5 or 10 LB increments. Fits weight stacks with guide rods that are 5" on-center (industry standard for nearly all weight stacks).