In modern transformer practice, the best protection against moisture ingress comes from fluoropolymer and high-performance elastomer materials rather than traditional rubber. For critical seals and gaskets, FKM (Viton), EPDM with low water permeability, and PTFE-based composites are widely used because they have very low diffusion rates for water vapor and good chemical stability in oil. For dynamic or flange seals, metal-reinforced gaskets with PTFE facing are common. In addition, silicone-based breather membranes and molecular sieve breathers are used to block atmospheric moisture, which is often more important than the gasket material itself.