This grease has very low a vapor pressure, highly inert, and nonflammable

Krytox LVP high vacuum grease is a combination of an extremely low vapor pressure perfluoroalkylpolyether oil and a fluorocarbon resin thickener. This white, buttery grease is designed to lubricate the fittings and accessories of high vacuum systems at operating temperatures down to 10-12 torr at 20°C (1.33 x 10-13 kPa).

The grease is for high-vacuum systems. Superior performance in laboratory and pilot plant equipment, as a lubricant and sealant for stopcocks, valves, fittings and o-rings operating at high vacuum or in hostile environments.