Traction-Tred® 1-3/4"W deeply serrated aluminum flat D-rung. Polyethylene rung wear sleeves. Combination aluminum rail end shield and shoe with extruded rubber slip-resistant shoe pad and steel spur plate. Twist-Proof® due to exclusive Alflo® rung joints. Pre-pierced holes at top of fly for field installation of accessories. For ladders 16'-32' rails are 3-1/2", flange 1-3/8" and D-rungs 1-3/4". For ladders 36' and 40' rails are 4", flange 1-3/4", and flat type D-rungs 1-3/4". Fly section width for 36'-32' ladders: 16-1/8" outside rail, 13-3/4" inside rails. Fly section width for 36' and 40' ladders: 16-3/4" outside rail, 13-1/4" inside rail. Base section for 16'-32' ladders 19-1/6" outside rail, 20-1/4" outside feet. Base section for 36' and 40' ladders 20-7/8" outside rail, 22" outside shoes. Meets ANSI and OSHA Standards. FOB Shipping Point.