D means that the product is rated in its category in terms of energy efficiency. The Energy Labeling system is based on EU Regulation 2017/1369/EU. D LG 20MK400H-B, 19.5", 1366 x 768 pixels, WXGA, LED, 5 ms, Black LG 20MK400H-B. Display diagonal: 19.5", Display resolution: 1366 x 768 pixels, HD type: WXGA, Display technology: LED, Display surface: Matt, Response time: 5 ms, Native aspect ratio: 16:9, Viewing angle, horizontal: 90°, Viewing angle, vertical: 65°. VESA mounting. Product color: Black