Molecular Sieve 13X is the sodium form of the type X crystal and has a much larger pore opening than the type A crystals. It will adsorb molecules with a kinetic diameter of less than 9 Angstrom (0.9 nm) and exclude those larger.
It also has the highest theoretical capacity of the common adsorbents and very good mass transfer rates. It can remove impurities too large to fit into a type A crystal and is commonly used to separate nitrogen from oxygen.