13 SOLID Plates each 180mm. Solid Plate Cathode & Solid Plate Anode.Resin Filled head (no leaks). Loose Screw cap to stop twisting plates. Replaces old cell with no adjustments. Solid plate is easier to clean. The calcium just falls off. Of the time compared to mesh cathode. In a cathode they last longer (as they have up to 3 times more material than mesh). There is no problem with using them in place of a mesh cell.