Econo grate Spiral Stair treads are available in steel, aluminum or
stainless steel and can be used on welded, standard kits or heavy duty model
stairs. This step works great for exterior applications, and as the name
states, it will not break the bank. ¼" x 3" slots fanning off the center of
the column not only offer excellent water drainage, but traction, and a
contemporary touch to the spiral staircase.