Apple weds high-res 4K visuals into its sleek 5mm thin 21.5" iMac with Retina 4K Display. With a 4096 x 2304 native resolution, this iMac provides 9.4 million pixels, which is 4.5 times more than the Full HD 1080p 21.5" iMac. The Retina 4K display also features a wider color gamut. Using a P3-based color gamut, the Retina 4K display provides a 25% larger color space than standard sRGB displays. And with more available colors, the images will appear more vivid and reveal greater detail.
This model has a 21.5" 4096x2304 LED-backlit 16:9 widescreen IPS DCI-P3 "Retina 4K" display (that runs "pixel doubled" to look like 2048x1152). The rear of the case is aluminum and is thicker in the middle and tapers to a razor thin 5 mm at the edges.