Liquid oxygen (also called Lox) has a pale blue color and is strongly paramagnetic: it can be suspended between the poles of a powerful horseshoe magnet. Liquid oxygen has a density of 1.141 g/cm3 and is cryogenic with a freezing point of 54.36 K and a boiling point of 90.19 K at 101.325 kPa. Liquid oxygen has an expansion ratio of 1:861 under 1 standard atmosphere and 20 °C (68 °F). Because of this, it is used in some commercial and military aircraft as transportable source of breathing oxygen.