Is it possible to show in the front end only the available attributes?

e.g. I sell rings in 3 sizes (#6,#7,#8) and #8 is out of stock.

For now my customer can still add #8 to cart and only when he enters "Shopping cart" or "Checkout" he's being announced that this item is "out of stock" .

I want that when he's shopping, he'll see only the available #6, #7 sizes. (customer shouldn't even know of the possibility of #8)

[I'm sure it's possible since before convincing the boss to move to ZenCart we had this functionality in a CRELoaded store:

Thank you very much