It is. That is why it is used in aviation, aerospace, and even automotive. Krytox is resistant to most harsh chemicals, that’s why the inertness of the product makes it great for sealants. It is somewhat waterproof; most the chemicals will not affect it. For fuel lines, it is extremely good with the temperature ranges. It can handle high or low temperatures resulting in things expanding or contracting. It’s also an excellent lubrication and grease for that.