PLUS 20 PLUS 20 IS DOUBLE DISTILLED AND OFFERS A COMBINATION OF LOWER VAPOR PRESSURE AND GREATER RESISTANCE TO OXIDATION. DOUBLE DISTILLATION LOWERS VAPOR PRESSURE BY REMOVING LIGHT END OIL FRACTIONS THAT CAN CAUSE BACKSTREAMING. THIS QUALITY MAKES PLUS 20 IDEAL FOR DIRECT DRIVE PUMPS USED IN BACKING DIFFUSION OR TURBOMOLECULAR PUMPS.