Draw a spiral staircase to any height and inner radius. Set the included angle (in plan), start angle and minimum riser height. Set the desired tread width, depth and thickness, and whether to omit the top step. Choose the radius and height of central pole, and whether or not to hide it. Set baluster height, width and depth, and rail diameter. Choose to show or hide inner and/or outer railing. Finally, choose direction of rotation of the stairs - up to the right or up to the left. The component works in both Imperial/US Customary and Metric units, depending on your model units.