Apiezon Type M Vacuum Grease is a good and economical high-vacuum grade lubricant. Initial pump down characteristics, at room temperature, are excellent. This is clearly the world's most widely used vacuum grease in electron microscope laboratories including use in both the electron microscope itself and the ancillary vacuum evaporator equipment. However, being completely hydrocarbon based completely free of silicones and halogens, there is some contribution to column contamination. Vapor pressure 2x10-9 torr at 20° C. Not intended for use where temperatures exceed 30° C. Apiezon L and M greases have strong powers of absorption, particularly for other hydrocarbon molecules due to their complex hydrocarbon structure and very high molecular weight. They are frequently used as the stationary phase in gas chromatography. Apiezon greases L and M have been especially formulated to provide excellent lubrication while maintaining an efficient gas seal and are widely used in the manufacture and servicing of high performance vacuum pumps. Apiezon vacuum greases have gained many prestigious approvals. Apiezon L grease, for example, is approved by The European Space Agency, Matra Marconi, NASA and NATO, while M grease is approved by NATO and N grease is approved by NASA and the US Navy.