JIS 10K is a flange standard published by the Japanese Standards Association (JSA). The standard size for a JIS 10K flange is JIS B 2220/2239-2006. 

JIS stands for Japanese Industrial Standard, and the JSA is the equivalent of the United States' ANSI. The Committee of the Japanese Industrial Standards (JISC) is responsible for creating and updating JIS standards. 

JIS 10K flanges are used in a variety of applications, including: Heavy oil refineries, Nuclear power, and Petrochemicals and acids. 

JIS 10K flanges are available in a variety of materials, including stainless steel, carbon steel, and alloy steel. Some types of JIS 10K flanges include: rjt flanges, blind flanges, weld neck flanges, slip on flanges, and socket weld flanges.