This is a replacement inverter board for the 20-inch iMac G5. This controls the backlight for the LCD. There are three main revisions of the iMac G5 20". There is the original, the ambient light sensor (ALS) model, and the iSight model. The inverter boards are not interchangeable, so be aware when choosing the option that you'll need to know which model you have. The images of each are available in the detailed images.