Why is 3a the standard for cls sieve instead of AA?

[ScoobyDoobie]

I think I remember someone saying that heptane can actually get bound up in 4a mol sieve but cant remember who said it.

Edit: I was wrong its 5a and it was @SkyHighLer

@SkyHighLer

Type 5A sieves. A crystalline calcium aluminosilicate with a pore size of about 5 Angstroms, these sieves adsorb larger molecules than type 4A. For example, as well as the substances listed above, propane, butane, hexane, butene, higher n-olefins, n-butyl alcohol and higher n-alcohols, and cyclopropane can be adsorbed, but not branched-chain C^ hydrocarbons, cyclic hydrocarbons such as benzene and cyclohexane, or secondary and tertiary alcohols, carbon tetrachloride or boron trifluoride. This is the type generally used for drying gases, though organic liquids such as THF and dioxane can be dried with this type of molecular sieves.