The 21.5" iMac Desktop Computer from Apple is an all-in-one desktop computer with an ultra-slim unibody design. Measuring at just 5mm at its edges, the iMac has 40% less volume than the 2011 iMac. The body of the iMac isn't the only thing that got thinner. The LCD display is now 5mm thinner, and Apple also removed a 2mm gap between the LCD panel and the glass to save even more space.