http://www.flanges-fittings.com/backing-rings/
Backing rings
Material: Ductile iron, carbon steel, stainless steel
Coatings: Antirust paint, epoxy paint, hot dipped galvanized, fusion bounded epoxy resin, Dacromet coating
Flange drilling: ANSI 150# / DIN/EN PN10
Pressure: SDR7, SDR11
Size: 1" to 48"