Helvetica is a neo-grotesque or realist design, one influenced by the famous 19th century typeface Akzidenz-Grotesk and other German and Swiss designs. Its use became a hallmark of the International Typographic Style that emerged from the work of Swiss designers in the 1950s and 60s, becoming one of the most popular typefaces of the 20th century. Over the years, a wide range of variants have been released in different weights, widths and sizes, as well as matching designs for a range of non-Latin alphabets. Notable features of Helvetica as originally designed include a high x-height, the termination of strokes on horizontal or vertical lines and an unusually tight spacing between letters, which combine to give it a dense, compact appearance.