... rings is widely used in petroleum, wellhead products,gate valve,flange,etc. StandardApplicationshapeAPI 6A,ISO 90012000,ISO9001 2008,ANSI ... etccasing head,flange, gate valve, oil&gas industry, oil christmas tree,wellhead assembly, ... ,etc)2) Valve (FC/FLS gate valve, mud gate valve, chock valve, etc)3) Fitting(union, manifold,elbows),bops. Standard Sealing Ring Gasket ...