Chrome plated weight stack selector shaft has 20 holes plus top plate mounting hole. A 3/8" diameter roll pin is used to mount the top plate to the selector shaft. Can be used to build a weight stack with a total of 21 plates including top plate. Will work interchangeably with either a 5 lb or 10 lb top plate, and your choice of 5 lb, 10 lb, 15 lb, or 20 lb weight stack plates. The top plate end of the shaft has a 1/2-13 female coarse threat for cable mounting hardware. The bottom end of the shaft is machined to a conical point. The diameter of the shaft is 7/8".