The most common and most important cryptand is ; the systematic IUPAC name for this compound is 1,10-diaza-4,7,13,16,21,24-hexaoxabicyclo[8.8.8]hexacosane.  This compound is termed [[2.2.2-Cryptand|[2.2.2]cryptand]], where the numbers indicate the number of ether oxygen atoms (and hence binding sites) in each of the three bridges between the amine nitrogen caps. Many cryptands are commercially available under the tradename Kryptofix.  All-amine cryptands exhibit particularly high affinity for alkali metal cations, which has allowed the isolation of salts of K.