Also called hydrogenated nitrile or highly saturated nitrile, HNBR is Buna-N rubber that’s modified with hydrogen to boost its performance. These sheets can handle higher heat and more pressure than standard Buna-N sheets, and they’re less likely to warp or rip. They’re also more resistant to oil, fuel, and chemicals—even mixtures of oil and heavy metals that would quickly wear out other rubbers. Often used in crude oil refineries, these sheets can be made into seals that withstand intense heat and pressure to contain dangerous materials. They’re not as heat-resistant as silicone, but they hold up better to wear and tear.