16K 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, 16K means 16KG pressure, 16K flange is medium pressure flange in JIS B2220 and KS B1503 flange series but also popular using, the flange type SOP SOH and Blind both have 16K pressure.