This window air conditioner support bracket is constructed from high-quality steel with a rust-resistant coating, supporting up to 300 lbs. to safely hold 5,000-24,000 BTU window AC units and remaining stable in harsh weather. It uses a drill-free multi-section support structure that evenly distributes the AC's weight, leaving no visible marks on windowsills or walls, making it well-suited for rental properties, apartments and historic buildings. The bracket has an extendable arm with adjustable width from 31.5 to 41.7 in. and leg length from 10.2 to 13.8 in., compatible with most single and double-hung windows with openings ranging 21-39 in., and works only on solid walls including concrete, brick, stone and solid wood, not vinyl frames or hollow aluminum frames. It features rotatable anti-slip pads on the legs to boost stability and cut down on operating noise, plus a magnetic level to ensure precise leveling during installation. No drilling, extra tools or ladders are needed, and 1 person can finish the entire installation in minutes with the included full mounting hardware, detailed illustrated instructions and an installation tutorial video.