Lightweight but sturdy. Spans 2 rungs for maximum support and stability. Will fit round or flat step rungs and mounts on inner or outer front ladder faces. Adjustments made quickly and easily with wing nut lock. Long body accepts up to 20" wide stages and planks. Short body accepts up to 14" wide stages and planks. UL listed and labeled. Recommended for use with 300 lb, Type IA extension ladders. OSHA and ANSI allow use with 250 lb, Type I extension ladders also. Package contains 1 pair of ladder jacks.