S.R. Smith- Ladder Step, High-Impact Plastic Vertical, 18 Inch Center to Center, 3 Inches Wide, No Hardware This replacement vertical ladder treads are used on pool ladders and diving towers These S.R. Smith steps are molded high-impact plastic. They are 3 wide and 18 Center to Center. Recommended for light-duty. Fits 1.9 O.D. rails. Purchase hardware bolts separately