Buyers must prioritize material grade, typically Ductile Iron (GGG40/50) or Stainless Steel (304/316), to ensure pressure resistance. The pressure rating (PN10, PN16, or PN25) must align with the existing pipeline system. Additionally, verify the drilling standard (such as EN1092, ANSI B16.5, or BS4504) to ensure the flange face matches your equipment perfectly. For the sealing component, EPDM or NBR gaskets are essential for leak-proof performance, depending on whether the medium is water, oil, or gas.