The size you need for your project will depend on the following information: Technological details needed: Projector light path on glass- measure how far away you are planning to place your projector from the glass. Use throw and aspect ratio as guidelines for your specific setup to determine the minimum size needed to clear your Lightpath. If you will be buying a framed unit – add 5” to the minimum size needed to clear the light path – 3” will be used for framing, 2” will be used as a cushion in the event you need to adjust/recalibrate your image. Architectural Details Needed: Pre-existing frame/hole in the wall: Determine if you can just replace the glass or if you will need a larger area frame. If you just need to upgrade the glass you have (either not anti-reflective or the current glass is damaged) you can simply replace the glass. If you need a frame to be made, measure the rough opening you have. The frame will be made to fit that space.