Molecular Sieve 13X is the sodium form of the type X crystal and has a much larger pore opening than the type A crystals.
Molecular Sieve 5A is an alkali aluminosilicate; it is the calcium form of the Type A crystal structure. Type 5A has an effective pore opening of 5 angstroms (0.5 nm).
Molecular Sieve 4A is an alkali aluminosilicate; it is the sodium form of the Type A crystal structure.
Molecular Sieve 3A is an alkali metal aluminosilicate; it is the potassium form of the type A crystal structure.