In the fall of 2007, Apple first introduced the aluminum iMac making it available on a 20-inch and a 24-inch iMac. In 2004 the previous version was a plastic design of the iMac, which was available in 17 -inch & a 20-inch design & a 24-inch screen. There were only 3 years between the White plastic iMac G5 & the aluminum iMac in 2007 a quick turnaround for a major redesign of a Mac. The aluminum front face is still a stark difference from the sleek aluminum front. Apple in 2009, overhauled its iMac lineup once again with an aluminum unibody design in 21.5 inches and 27 inches introducing the two screen sizes that are still in use today. Apple has not redesigned the iMac since 2009. Apple in 2012, redesigned the iMac with an ultra-slim side profile and removed the SuperDrive. In 2015, the iMac was upgraded with a Retina display. All the iMac have stayed the same with aluminum build with black bezels and an aluminum chin. The last significant update to the iMac was the introduction of the unibody aluminum design in 2009, but even that changeover actually started in 2008.