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