This range of Ultragrade® oils replaces all previous types and gives improved vacuum performance. Ultragrade 15 should be selected for small pumps or for cold start applications. Ultragrade 19 is suitable for all mid-range pumps, including those used with electron microscopes and evaporation systems. For large booster pumps, or where corrosive gases are encountered, Ultragrade 20 should be used. Pfeiffer P3 oils are used in pumps supplied with the Agar coating units.