1-1/2" flat top rung for sure footed comfort. 2-3/4" modified I beam side rail on 16' thru 24', 3"I beam side rail on 28' thru 40'. Only 6" from ground to first rung. Exclusive ALFLO hardened rung joint makes rungs spin-prooffor lifetime strength and safety. UL listed and labeled. 16' thru 32': 3' overlap, 40': 4' overlap. Rope and pulley on 20' and larger. Type III household duty rating 200 lb. load capacity.