Features: Fits wall thickness from 3"" to 15.2"" 17"" long A/C resting surface The support holds up to 180 pounds Support A/C BTU ratings of: 12,000 BTU-24,000 BTU Install Tips: a: Slide support leg into support rail and lock the support legs in desired position. b: Insert the included Square Tube into each side of the Tube Rail while pressing both spring bottons. Release bottons at the desired length. c: Place the bracket in window and adjust each sill Square Tube until it is positioned securely inside the window frame. D:Adjust the legs until the H-frame is tilted very slightly downward. Be sure the support foot pads are resting on the exterior. Place air conditioner on the bracket Window Requirements: 1.Window sill thickness cannot exceed 16 inches 2.Window sill must be a minimum of 2 inches deep 3.Window sill must be able to accept 2 1/2 inches long screws 4.Sliding window lip or window stool cannot exceed 1 7/8inches 5. Cannot be used with slide casement or casement windows Since it is a window sill operation, please pay attention to safety. Safety is first. Since it is a window sill operation, please pay attention to safety. Safety is first.