Radial Plate Spiral staircase step is available in mild steel, aluminum and stainless steel, and can be incorporated into all kit and fully assembled spiral stairs. Radial plate pattern was designed to replicate our radial grate tread, but cut out of 3/16" plate, giving this step a great price point, and very rigid feel. Tapering slots not only allow for drainage of snow and rain, but add a ton of traction, and aesthetic value to the spiral staircase.