For QRNF stubs
Flanges - ISO-DIN series.
Steel core backing ring, PP/FRP coated, according to EN/ISO/DIN for stubs QRV and QPV. Drilling: PN 10/16 up to DN 150; PN 10 from DN 200.
Those backing rings are specifically used for socket welding, for other diameters please refer to the ODT range.
