10K flange is a pressure rating for flange norms of JIS B2220 and KS B1503, the JIS B2220 and KS B1503 full pressure rating class are 5K 10K 16K 20K 30K 40K etc, 10K means 10KG pressure, 10K flange is low pressure flange in JIS B2220 and KS B1503 flange series but also popular using, the flange type SOP SOH and Blind both have 10K pressure.